Secondary Keywords: What They Are & How to Find Them

Most keyword research advice stops at "find a keyword, write about it." That's fine for the primary keyword. But a single keyword — no matter how well you optimize for it — rarely explains why one page outranks another for a competitive topic. The difference is usually secondary keywords: the supporting terms that show Google (and readers) you've actually covered the topic instead of just mentioning it.

This post defines secondary keywords precisely, clears up the confusion with LSI keywords and related keywords, and walks through a repeatable process for finding and using them — including how to do it on content you've already published.

What Are Secondary Keywords?

Secondary keywords are the additional search terms a page targets alongside its primary keyword. They're closely related to the main topic, often searched by the same audience, and typically have lower individual search volume than the primary term — but collectively they can drive as much or more traffic.

If your primary keyword is "email marketing software," secondary keywords might include "best email marketing tools for small business," "email automation platform," and "email marketing software pricing." Each represents a slightly different angle, question, or intent that a searcher interested in the primary topic might also have.

The key distinction: secondary keywords aren't just synonyms stuffed in for keyword density. They're terms that represent genuine subtopics, related questions, or variations in how people phrase the same underlying need. A page that only targets its primary keyword tends to read thin. A page that naturally works in secondary keywords tends to read complete — because covering those terms usually means covering the sub-questions a thorough answer requires.

Primary vs. Secondary Keywords: What's the Difference?

A primary keyword is the main search term you want a page to rank for. It's the term that best matches the page's core topic and the intent you're writing to satisfy. You typically choose one primary keyword per page, and it drives your title tag, H1, and URL slug.

A secondary keyword is a supporting term — related to the primary keyword, often lower volume individually, that you weave into the body content, subheadings, and occasionally the meta description. Secondary keywords don't replace the primary keyword's role; they reinforce and expand it.

Here's a simple way to think about the relationship: the primary keyword defines what the page is about. Secondary keywords define what the page actually covers. A page targeting "email marketing software" as its primary keyword but never mentioning pricing, automation features, or alternatives to well-known tools is missing the secondary keywords that signal genuine topical coverage — and probably missing the content those searchers wanted anyway.

One more practical difference: primary keywords usually get the most deliberate placement (title, H1, URL). Secondary keywords get placed more organically, wherever the topic naturally calls for them — in an H2, a comparison table, an FAQ answer. You're not trying to force every secondary keyword into a prominent slot; you're trying to make sure the content addresses what they represent.

Secondary Keywords vs. LSI Keywords vs. Related Keywords

This is where most explanations get muddy, so let's separate the three terms cleanly.

Secondary keywords are keywords you deliberately choose to target on a page because they represent distinct, related search queries with their own (even if small) search volume. You could type a secondary keyword into Google and get a results page. Example: if your primary keyword is "secondary keywords," a secondary keyword might be "how many secondary keywords should I use."

LSI keywords (Latent Semantic Indexing keywords) is a term that gets used constantly in SEO content but is based on a misunderstanding. LSI is an actual mathematical technique for analyzing term relationships in a corpus of documents — it's not something Google's modern ranking systems are known to use for keyword association in the way SEO folklore suggests. What people usually mean by "LSI keywords" is really just semantically related words and phrases — terms Google's language models associate with the topic based on context, not literal query overlap. There's no tool that outputs "real" LSI keywords; tools claiming to do so are generating semantic/related term lists and using outdated terminology.

Related keywords and semantic keywords are the more accurate, modern terms for what people mean by LSI. These are words and phrases that co-occur with your topic often enough that their presence signals topical depth and relevance — think "open rate," "unsubscribe rate," and "drip campaign" for a page about email marketing software. You don't necessarily target these as standalone ranking queries; you include them because their absence would make the content read as shallow or off-topic.

The practical distinction: secondary keywords are queries you could rank for independently. Related/semantic keywords are vocabulary that proves you know the topic, whether or not each one ever shows up in Search Console as a query. In practice, there's overlap — a related keyword sometimes has enough volume to function as a secondary keyword too. But treating "secondary keyword" and "LSI keyword" as interchangeable, which a lot of glossary content does, blurs a distinction that actually matters for how you use each one.

Why Secondary Keywords Matter for SEO

Secondary keywords matter for three concrete reasons, not just "more keywords = more traffic."

They capture additional search demand from one page. A well-optimized page doesn't rank for one query — it ranks for dozens, sometimes hundreds, of variations and related queries. Secondary keywords are the terms you deliberately account for so that additional demand isn't accidental; it's designed in. Pull up Search Console data for any ranking page and you'll typically see it capturing impressions for far more queries than the one you originally targeted.

They demonstrate topical relevance to Google's ranking systems. Modern search ranking evaluates whether a page thoroughly covers a topic, not just whether it repeats a phrase. A page about "secondary keywords" that never mentions primary keywords, keyword research, or search intent looks incomplete relative to one that naturally covers the surrounding topic. Secondary keywords are often just the vocabulary of genuine topical coverage, formalized into a list you can check against.

They reduce the risk of keyword cannibalization. When you map out primary and secondary keywords deliberately, you avoid a common failure mode: publishing multiple pages that all loosely target the same query because nobody defined which page owns which term. If "email marketing automation" is a secondary keyword on your "email marketing software" page, you shouldn't also be publishing a separate dedicated page trying to rank that same term as its primary target — you'll split relevance and possibly cannibalize your own rankings. This is exactly the problem Keyword Clustering is built to prevent: grouping keywords by shared search intent and SERP overlap before you write anything, so you know which terms belong on the same page as secondary support and which deserve their own page entirely.

The 4 Main Types of Keywords

Most keyword frameworks converge on four functional types:

1. Primary keywords — the main target for a given page; drives the title, H1, and URL.
2. Secondary keywords — supporting queries related to the primary keyword, addressed within the content.
3. Long-tail keywords — longer, more specific phrases (often three or more words) with lower search volume but higher intent specificity and typically less competition. A long-tail keyword can function as a secondary keyword, but not every secondary keyword is long-tail — "email automation" is short and could be secondary; "best email automation software for real estate agents" is long-tail and could also be secondary. The terms describe different properties (length/specificity vs. role on the page) and often overlap without being synonyms.
4. LSI/semantic keywords — related vocabulary and concepts that signal topical depth, as covered above.

Some frameworks also split keywords by intent (informational, navigational, commercial, transactional) as a separate, cross-cutting classification — worth knowing, but it answers a different question (what does the searcher want to do) than the four types above (what role does this keyword play in your content structure).

How to Find Secondary Keywords

Start with the SERP for your primary keyword. Search it, and look at what's already ranking. The "People Also Ask" box, the "related searches" at the bottom of the page, and the subheadings used by top-ranking pages are a fast, free source of secondary keyword candidates — because they reflect what Google already associates with the query.

Run keyword research tools against your primary keyword. Standard keyword research tools will return keyword variations, questions, and related terms with search volume attached. Filter for terms that share searcher intent with your primary keyword — not just terms that share words. "Email marketing software" and "email marketing jobs" share two words but represent completely different intents; only one belongs as a secondary keyword on a software comparison page.

Do a content gap analysis against competitors. Pull the top 5–10 ranking pages for your primary keyword and list every subheading and subtopic they cover. Terms that show up across most of them are strong secondary keyword candidates — they represent the baseline coverage expected for that topic. Terms only one or two competitors cover might be differentiators worth including, or might be off-topic noise; check search intent before assuming either.

Check Search Console query data for pages you've already published. This is the step most keyword research guides skip entirely, and it's one of the more useful things you can do with existing content. If a page is already live and getting impressions, open the Performance report, filter to that specific page, and look at every query it's getting impressions for. You'll typically find:

• Queries close to your primary keyword that you're getting impressions for but ranking poorly on — these are secondary keyword candidates you haven't explicitly addressed yet.
• Queries with decent impressions but a low click-through rate — often a sign the content touches the topic but doesn't answer it directly enough for that specific phrasing.
• Completely unexpected queries the page ranks for — sometimes these reveal a subtopic worth expanding into its own section, or occasionally a sign the page is drifting off-topic and picking up irrelevant impressions.

Take the queries with real impression volume that aren't yet addressed head-on in your content, and treat them as secondary keywords to add in a content refresh — a new H2, an expanded paragraph, or an FAQ entry. This turns Search Console from a reporting tool into a keyword discovery tool for content you've already invested in, rather than something you only consult before writing.

Use "also asked" and forum-style research for phrasing, not just topics. People Also Ask boxes and threads on forums like Reddit often surface the exact phrasing real searchers use, which can differ from what keyword tools suggest. This matters because a secondary keyword phrased the way people actually search ("why isn't my email deliverability improving") often converts better as a subheading than a stiffer, tool-generated equivalent ("email deliverability improvement factors").

How Many Secondary Keywords Should You Use?

There's no fixed magic number, but there is a workable rule of thumb: plan for roughly one secondary keyword per 150–250 words of body content, scaling with the depth of the topic rather than forcing a count.

A 1,500-word page might reasonably work in 6–10 secondary keywords across its subheadings and body copy. A 3,000-word guide might cover 15–20, simply because there's more room to address more subtopics without cramming. The number should come out of how many genuine subtopics the primary keyword requires to be fully answered — not from a target you decided on before outlining the content.

A better check than "how many" is "does each one earn its place." Every secondary keyword should map to a real section, question, or subtopic — not a sentence bolted on just to hit a term. If you can't point to the paragraph or H2 where a secondary keyword is substantively addressed, it's not actually integrated; it's just present, which is the difference between topical coverage and keyword stuffing.

How to Use Secondary Keywords in Your Content

Subheadings (H2s and H3s) are the highest-value placement. Structuring your content so that major secondary keywords each get their own subheading does two things: it signals to search engines that the page addresses that subtopic directly, and it gives readers a scannable way to find the section relevant to their specific question.

Body copy, used naturally. Secondary keywords should appear in the sentences that are actually about that subtopic — not sprinkled evenly throughout for density. If a secondary keyword only makes sense in one section, it should only appear in that section.

Meta description — selectively. The meta description doesn't carry direct ranking weight, but it does affect click-through rate from the search results page. Working a high-value secondary keyword into the meta description can help when that phrasing matches what a meaningful share of searchers are typing — because it visually confirms to the searcher that the page covers their specific angle, not just the general topic. Don't force it if it makes the description read awkwardly; a description that's clear and enticing beats one that's keyword-complete but clunky.

Title tag — usually not, and this is worth being direct about. The title tag's primary job is to precisely match the primary keyword and search intent. Cramming a secondary keyword into the title tag usually dilutes relevance signal for the primary term without meaningfully improving how the page ranks for the secondary one — that ranking is driven much more by whether the secondary keyword's underlying question is thoroughly answered in the body. The exception is when a secondary keyword is close enough to the primary that including it strengthens rather than dilutes the title (e.g., primary "email marketing software," secondary "email marketing tools" — near-synonymous enough that both fit naturally). If they're not that close, leave the title tag focused on the primary keyword and let the secondary keyword do its work in the H2s and body.

Image alt text, when relevant. If an image illustrates a specific subtopic, its alt text is a reasonable, low-effort place for the associated secondary keyword — again, only when it accurately describes the image.

Secondary Keywords Examples

Abstract explanations only go so far. Here's a full worked example, mapping one primary keyword to a realistic set of secondary keywords, the way you'd actually plan a page.

Primary keyword: "project management software"

Secondary keyword	Where it fits
best project management software for small teams	H2 — comparison/recommendation section
project management software pricing	H2 — pricing breakdown section
free project management tools	H2 or subsection — addresses budget-conscious intent
project management software vs. spreadsheets	H2 — comparison for undecided searchers
Gantt chart software	Body mention within a features section
project management software for remote teams	H2 — use-case-specific section
project management tool integrations	Body mention within a features section

Notice that none of these are synonyms for "project management software" — they're distinct angles a real buyer researching the category would search for at some point in their decision process. That's the pattern to replicate, not the specific terms.

Here's the same pattern in a completely different industry, to show it generalizes:

Primary keyword: "commercial roof inspection"

Secondary keyword	Where it fits
how often should a commercial roof be inspected	H2 — frequency/maintenance schedule section
commercial roof inspection checklist	H2 — process/what's-included section
commercial roof inspection cost	H2 — pricing section
signs your commercial roof needs repair	H2 — problem-identification section
commercial roof inspection for insurance claims	H2 — use-case section
flat roof vs. sloped roof inspection	Body mention within methods section

In both examples, the secondary keywords aren't padding — each one represents a question the primary keyword's audience actually has, at a different stage of research or decision-making. That's the test for whether a term deserves to be a secondary keyword: does it represent a real subtopic this searcher would want answered, or is it just a rephrasing that doesn't add coverage.

Tools to Find and Generate Secondary Keywords

Standard keyword research tools (the ones offering search volume, keyword difficulty, and "related keywords" or "questions" reports) are the starting point for most people doing this manually — they're useful for volume data and initial discovery, less useful for figuring out how those terms should be grouped and distributed across pages.

That grouping step is where a lot of manual keyword research breaks down. It's easy to end up with a spreadsheet of 80 loosely related keywords and no clear answer to which ones belong on the same page versus which ones need their own dedicated page. That's the specific problem Keyword Clustering solves — it groups keywords by actual SERP overlap and shared search intent, so you're not guessing whether "project management software pricing" belongs as a secondary keyword on your main page or deserves its own dedicated pricing page. We've written more on how this works and why SERP overlap is the right signal to cluster on, not just semantic similarity, in our piece on keyword clustering and SERP overlap.

Once you know your primary keyword and the secondary keywords you want it to cover, the harder problem is usually writing content that addresses all of them credibly — not superficially touching each one, but actually answering the question each represents, in a page that still reads coherently as one piece of content. This is where we built our AI SEO Content Writer to do something more specific than generate generic prose: it runs live SERP research on the primary keyword before writing anything, identifies the subtopics and secondary keywords that top-ranking pages actually cover (not a generic keyword list), and builds an evidence-based content brief from that research. The result is content structured around subheadings that map to real secondary keywords and questions — grounded in what's currently ranking, not a guess at what might be relevant. It won't invent secondary keywords that have no basis in actual search behavior, and it won't stuff them in past the point where they serve the reader — the brief is built to reflect genuine topical coverage, not a keyword count to hit.

Search Console, mentioned earlier, is the underused tool in this list — not for finding new keyword ideas in a vacuum, but for finding secondary keyword opportunities specific to a page you've already published, based on real queries it's already getting impressions for.

Common Mistakes to Avoid with Secondary Keywords

Treating secondary keywords as synonyms to repeat, not subtopics to cover. The most common mistake is writing a section that just rephrases the same sentence three different ways to work in three "secondary keywords" that are really just word-order variations of the primary term. This doesn't add coverage — it adds redundancy, and it reads badly. A real secondary keyword should require you to write something you haven't already said.

Over-stuffing for density instead of covering intent. If you're checking a keyword density percentage and inserting secondary keywords until you hit it, you're optimizing for the wrong signal. Density has never been a reliable proxy for relevance; thorough, accurate coverage of the subtopic is. A page can mention a secondary keyword once, in the right context, and rank for it — because the ranking system is evaluating whether the question was answered, not how many times the phrase appears.

Choosing secondary keywords with mismatched intent. Not every keyword that shares words with your primary keyword shares its intent. "Best CRM software" and "CRM software jobs" both contain "CRM software," but only one belongs on a buyer's-guide page. Before adding any secondary keyword, check what's actually ranking for it — if the top results are a completely different content type (job listings vs. product comparisons), it's the wrong secondary keyword for your page, regardless of volume.

Writing a "false-synonym" section just to hit a keyword. This is a specific version of the stuffing mistake worth calling out on its own: creating an entire H2 section around a secondary keyword that's really a near-duplicate of another section you already wrote, just to have a subheading with that exact phrase in it. Readers notice the redundancy even if they can't articulate why the page feels padded. If two secondary keywords represent close to the same underlying question, address them together in one well-developed section rather than splitting them into two thin ones.

Ignoring cannibalization risk across your own site. If you're adding a secondary keyword to Page A, check whether Page B on your site is already trying to rank that term as its primary keyword. If so, you're now competing with yourself. This is avoidable with upfront keyword clustering — but it's just as important to check when you're updating existing content, not only when planning new pages.

Forgetting to revisit secondary keywords after publishing. Keyword research typically happens once, before writing. But search behavior around a topic shifts, and Search Console will show you new query patterns months after publishing that didn't exist (or weren't visible) at the research stage. Treat secondary keyword research as something to revisit during content refreshes, not just at the outline stage.

Secondary keywords aren't a checkbox to tick after you've written your primary-keyword-focused draft — they're a reflection of whether your content actually covers the topic the way the people searching for it need it covered. Get the primary keyword right, get the secondary keywords right, and the ranking signal tends to follow the coverage rather than the other way around.