SEO Dictionary: 50 Terms That Matter

An SEO dictionary is a reference guide to the terminology used in search engine optimisation, covering the concepts, metrics, and technical language practitioners use when building and measuring organic search performance. This one is built differently. Rather than listing every term alphabetically with textbook definitions, I’ve focused on the 50 terms that come up most often in real strategy conversations, the ones where a vague understanding creates real problems.

If you’ve ever sat in an SEO briefing and nodded along while quietly unsure what crawl budget or topical authority actually means in practice, this is the reference you needed in that room.

Why Terminology Gaps Cost You More Than You Think

Early in my career, I watched a client presentation fall apart because the agency team and the client’s in-house team were using the same words to mean completely different things. “Authority” meant domain-level trust signals to one side and brand reputation to the other. The resulting strategy tried to serve both interpretations and served neither particularly well.

That kind of misalignment is more common than people admit. When I was running agency teams across 30 industries, the briefing process was often where the real problems started. Not because people were uninformed, but because SEO vocabulary is genuinely inconsistent. Google uses certain terms in specific ways. Third-party tools use different definitions for similar-sounding metrics. And practitioners often develop their own shorthand that doesn’t travel well across teams.

This dictionary is designed to close those gaps. If you’re building a broader understanding of how organic search works as a commercial channel, the Complete SEO Strategy hub is where the surrounding context lives.

Core Search Concepts

Algorithm , The system Google uses to assess and rank web pages. It is not a single rule but a collection of interconnected systems, many of which run simultaneously. When people say “the algorithm changed,” they usually mean Google updated one or more of these systems.

Core Update , A significant change to Google’s ranking systems, typically affecting a broad range of queries and sites rather than targeting a specific behaviour. Core updates often cause ranking volatility and can take weeks to fully settle.

Crawling , The process by which search engine bots (called crawlers or spiders) discover and read web pages by following links. Crawling is the first step before a page can be indexed or ranked.

Crawl Budget , The number of pages a search engine will crawl on your site within a given timeframe. On large sites with thousands of pages, crawl budget matters. If Google is spending its crawl allocation on low-value pages, your important content may not get crawled as frequently as it should.

Indexing , The process of storing and organising crawled content in Google’s database. A page must be indexed before it can appear in search results. Crawling does not guarantee indexing. Google can crawl a page and decide not to index it.

Rendering , The process by which Google executes a page’s code (including JavaScript) to understand what users would actually see. Sites that rely heavily on JavaScript for content delivery can have rendering delays that affect how quickly content is indexed.

SERP , Search Engine Results Page. The page Google returns in response to a query. Modern SERPs contain far more than ten blue links: featured snippets, image carousels, People Also Ask boxes, local packs, shopping results, and AI-generated summaries all compete for attention above and below traditional organic listings.

Search Intent , The underlying goal behind a search query. Google categorises intent broadly as informational (wanting to learn), navigational (wanting to find a specific site), commercial (researching before buying), or transactional (ready to act). Matching your content to the correct intent type is more important than keyword density.

Query , The actual words a user types into a search engine. Queries and keywords are related but not identical. A keyword is what you target; a query is what users actually type, which may be phrased differently.

Search Volume , The estimated number of times a keyword is searched per month. Search volume is useful for prioritisation but should never be treated as a traffic guarantee. A page ranking first for a 1,000-volume keyword will not receive 1,000 visits per month. Click-through rates, SERP features, and seasonal variation all affect actual traffic.

Ranking Signals and Factors

Ranking Factor , A confirmed signal that Google uses to determine where a page ranks. Google has confirmed relatively few of these explicitly. Many things practitioners call ranking factors are better described as ranking signals or correlations observed in studies.

Ranking Signal , A broader term for any input that may influence rankings. The distinction from ranking factor matters: signals include things Google may weigh differently depending on the query, the site, or the competitive landscape. Not all signals are equal, and not all apply to every situation.

E-E-A-T , Experience, Expertise, Authoritativeness, and Trustworthiness. A framework from Google’s Search Quality Rater Guidelines used to assess content quality. It is not a direct ranking factor in the algorithmic sense, but it reflects the qualities Google’s systems are designed to reward. For competitive or sensitive topics, E-E-A-T alignment is increasingly important.

Page Experience , A set of signals Google uses to assess how users experience a page beyond its content. This includes Core Web Vitals, mobile-friendliness, HTTPS, and the absence of intrusive interstitials. Page experience is a tiebreaker in competitive rankings, not a primary driver.

Core Web Vitals , Three specific metrics Google uses to measure page experience: Largest Contentful Paint (loading performance), Interaction to Next Paint (interactivity), and Cumulative Layout Shift (visual stability). These are measurable and actionable, which makes them useful, but improving them rarely produces dramatic ranking changes on their own.

Freshness , A signal Google uses to favour recently updated or published content for queries where recency is relevant, such as news, trending topics, or time-sensitive searches. For evergreen content, freshness is less critical than depth and authority.

On-Page and Content Terms

Title Tag , The HTML element that specifies the title of a page. It appears in browser tabs and, usually, as the clickable headline in search results. Google may rewrite title tags if it determines they don’t accurately represent the page content. Keeping title tags accurate, descriptive, and under 60 characters reduces the likelihood of rewrites.

Meta Description , A short HTML summary of a page’s content. It does not directly influence rankings but affects click-through rate when displayed in search results. Google may replace it with a snippet it generates from page content, particularly if your meta description doesn’t match the query well.

Header Tags , HTML elements (H1 through H6) used to structure page content. H1 is the main page heading. H2 and H3 are used for sections and subsections. Proper use of header tags helps both users and search engines understand content hierarchy.

Keyword Density , The percentage of times a keyword appears relative to total word count. This was a significant optimisation metric in early SEO. It is largely irrelevant now. Writing naturally for the reader while covering a topic thoroughly produces better results than targeting a specific density percentage.

Semantic SEO , An approach to content that focuses on topics, concepts, and the relationships between them rather than exact keyword repetition. Google’s ability to understand meaning and context has made semantic relevance more important than literal keyword matching.

Topical Authority , The degree to which a site is recognised as a credible, comprehensive source on a specific subject. Building topical authority means covering a topic in depth and breadth, not just targeting individual keywords in isolation. It’s one of the more commercially important concepts in modern SEO strategy and one that gets underweighted in short-term planning.

Featured Snippet , A selected search result that appears at the top of the SERP in a formatted box, above the standard organic listings. Google pulls featured snippet content from a page it judges to have answered the query clearly and directly. Optimising for featured snippets involves structuring answers concisely and matching the format (paragraph, list, or table) that Google tends to use for that query type.

Schema Markup , Structured data code added to a page to help search engines understand its content more precisely. Schema can enable rich results in the SERP, such as FAQ accordions, review stars, and event details. It doesn’t guarantee rich results, but it makes them possible.

Thin Content , Pages with little substantive value, either due to low word count, duplicated content, or content that doesn’t meaningfully address the user’s query. Google’s Panda update (now integrated into the core algorithm) was designed to reduce thin content in rankings. Sites with high proportions of thin pages can see sitewide ranking suppression.

Content Cannibalization , A situation where multiple pages on the same site compete for the same keyword, confusing search engines about which page to rank. The result is often that neither page ranks as well as a single, consolidated page would. I’ve seen this problem on sites with hundreds of blog posts where the content strategy was volume-first and intent-second.

Technical SEO Terms

Robots.txt , A text file in a site’s root directory that instructs search engine crawlers which pages or sections they should not crawl. Misconfigurations in robots.txt can accidentally block important pages from being crawled. It’s one of the first things I check during a technical audit.

Canonical Tag , An HTML element that tells search engines which version of a page is the “master” version when similar or duplicate content exists across multiple URLs. Canonical tags are commonly used on e-commerce sites where product pages may be accessible via multiple URL paths.

301 Redirect , A permanent redirect from one URL to another. When a page moves or is deleted, a 301 redirect passes most of the original page’s ranking signals to the new destination. Using temporary (302) redirects when you mean permanent ones is a common technical mistake with ranking consequences.

Sitemap , An XML file that lists the pages on a site and provides metadata about them (such as last updated date and priority). Submitting a sitemap to Google Search Console helps ensure important pages are discovered and crawled efficiently.

Hreflang , An HTML attribute used to indicate to search engines which language and regional version of a page should be served to users in different locations. Essential for multinational sites. When implemented incorrectly, it can cause the wrong language version to rank in the wrong market.

Log File Analysis , The process of examining server log files to understand how search engine bots are actually crawling a site, as opposed to how you think they are. Log file analysis reveals crawl frequency, which pages bots visit most, and where crawl budget is being wasted. It’s underused and often more revealing than crawl simulation tools.

Site Architecture , The structure of a website, specifically how pages are organised and linked to each other. Good site architecture ensures that important pages are reachable within a small number of clicks from the homepage and that internal link equity flows to the pages that matter most commercially.

URL Structure , The format and organisation of a page’s web address. Clean, descriptive URLs that include relevant keywords perform better than long, parameter-heavy strings. This matters both for user experience and for how search engines interpret page context.

Link-Related Terms

Backlink , A link from an external website pointing to your site. Backlinks remain one of the most significant signals in Google’s ranking systems. Not all backlinks are equal. A single link from a highly authoritative, topically relevant site is worth more than dozens of links from low-quality directories.

Internal Link , A link from one page on your site to another page on the same site. Internal links distribute authority across your site, help search engines understand content relationships, and guide users to related content. Internal linking strategy is often underinvested relative to its impact.

Anchor Text , The visible, clickable text of a hyperlink. Anchor text provides context to search engines about what the linked page is about. Over-optimised anchor text (using exact-match keywords repeatedly) can trigger spam signals. Natural variation is both safer and more credible.

Link Equity , Sometimes called “link juice,” this refers to the value or authority passed from one page to another through a hyperlink. Pages with more inbound links from authoritative sources accumulate more link equity, which can then be distributed to other pages via internal links.

Nofollow , An attribute added to a link to signal that the linking page does not want to pass ranking credit to the destination. Google treats nofollow links as hints rather than directives. Links in user-generated content, comments, and paid placements should typically be nofollowed.

Link Profile , The overall collection of backlinks pointing to a site, assessed in terms of quantity, quality, diversity, and anchor text distribution. A healthy link profile includes links from a range of domains, with varied anchor text and a mix of followed and nofollowed links.

Disavow , A tool in Google Search Console that allows site owners to ask Google to ignore specific backlinks. It exists for situations where a site has acquired genuinely harmful links it cannot get removed. It’s often overused by practitioners who disavow low-quality links that are simply neutral rather than harmful.

Authority and Trust Metrics

Domain Authority (DA) , A metric developed by Moz to predict how well a site might rank in search results, scored from 0 to 100. It is not a Google metric. Google does not use Domain Authority in its ranking systems. It’s a useful proxy for comparing sites, but treating it as a ranking truth is a category error I’ve seen cause poor link-building decisions repeatedly. Moz’s own guidance on SEO investment is more nuanced than the metric itself suggests.

Domain Rating (DR) , Ahrefs’ equivalent metric to Domain Authority. Same caveat applies: it’s a third-party proxy, not a Google measurement. Useful for relative comparison, not absolute truth.

PageRank , Google’s original algorithm for assessing page-level authority based on the quantity and quality of links pointing to a page. Google no longer publicly shares PageRank scores, but the underlying concept of link-based authority still forms a significant part of how Google assesses pages.

Trust Flow / Citation Flow , Majestic’s metrics for assessing link quality and quantity respectively. Again, third-party proxies. Useful for competitive benchmarking, not gospel.

Keyword Research Terms

Head Term , A short, high-volume, broadly competitive keyword, typically one or two words. Head terms are difficult to rank for and often have mixed intent. They generate traffic but not always qualified traffic.

Long-Tail Keyword , A longer, more specific keyword phrase with lower search volume but higher specificity. Long-tail keywords typically convert better because the searcher’s intent is clearer. For newer sites or those in competitive categories, long-tail targeting is often the more commercially sensible starting point.

Keyword Difficulty , A metric used by SEO tools to estimate how hard it would be to rank for a given keyword based on the strength of current ranking pages. Keyword difficulty scores vary significantly between tools. Treat them as directional, not definitive.

Keyword Mapping , The process of assigning specific target keywords to specific pages on a site. Good keyword mapping prevents cannibalization, ensures each page has a clear purpose, and creates a logical structure that matches how users search across different stages of their decision-making.

SERP Features , Non-standard elements that appear in search results beyond the ten blue links. These include featured snippets, People Also Ask boxes, image packs, local packs, knowledge panels, and shopping results. Understanding which SERP features appear for your target keywords affects how you should structure content and what kind of traffic you can realistically expect.

Measurement and Analytics Terms

Organic Traffic , Visits to a site that arrive through unpaid search results. Organic traffic is measured in analytics platforms, but the number you see is not a complete picture. Dark traffic (direct visits that are actually from search), bot traffic, and attribution model differences all affect what organic traffic figures actually represent.

Click-Through Rate (CTR) , The percentage of people who see your listing in search results and click on it. CTR is visible in Google Search Console and is affected by your title tag, meta description, SERP position, and the presence of competing SERP features. A high-ranking page with a poor CTR is a straightforward optimisation opportunity.

Impressions , The number of times your page appeared in search results for a given query, regardless of whether it was clicked. Impressions data in Search Console is useful for identifying keywords where you’re visible but not converting to clicks.

Average Position , The mean ranking position of a page across all the queries it appears for. Average position is a blunt metric. A page with an average position of 8 might rank 1 for some queries and 30 for others. Segment by query type before drawing conclusions.

Bounce Rate , The percentage of sessions where a user lands on a page and leaves without visiting another page. In Universal Analytics, a high bounce rate was often misread as a sign of poor content. In many cases, users found exactly what they needed and left satisfied. Context matters more than the number.

Conversion Rate , The percentage of visitors who complete a desired action. SEO should in the end be measured by the quality of the audience it delivers, not just its volume. When I was managing large-scale paid and organic programmes simultaneously, the channels that generated the most traffic were rarely the ones generating the most commercial value. Organic search was often the exception, but only when the keyword strategy was built around intent rather than volume.

Advanced and Emerging Terms

Entity , A distinct, identifiable concept, person, place, or thing that Google can recognise and understand independently of specific keyword strings. Google’s Knowledge Graph is built on entities and the relationships between them. As Google’s understanding of entities has matured, optimising for entity recognition (through structured data, consistent brand mentions, and authoritative citations) has become increasingly relevant, particularly for brand-level SEO.

Knowledge Graph , Google’s database of entities and the relationships between them. When Google displays a knowledge panel in the SERP for a brand, person, or organisation, it’s drawing from the Knowledge Graph. Getting your brand accurately represented in the Knowledge Graph requires consistent, accurate information across authoritative sources.

Search Generative Experience (SGE) / AI Overviews , Google’s AI-generated summaries that appear at the top of some search results. These pull from multiple sources and can reduce click-through rates for informational queries. The commercial implications are still playing out, but sites with strong topical authority and clear, well-structured content appear to be cited more frequently in AI-generated responses.

Zero-Click Search , A search query where the user finds the answer directly in the SERP without clicking through to any website. Featured snippets, knowledge panels, and AI Overviews all contribute to zero-click behaviour. Search Engine Journal’s analysis of search engine loyalty provides useful context on how user behaviour around search is evolving. For SEO strategy, zero-click searches are a reason to think carefully about which queries you invest in ranking for and what the actual traffic opportunity looks like.

Passage Indexing , Google’s ability to index and rank specific passages within a page, not just the page as a whole. This means a single page can rank for multiple queries if it contains distinct, well-structured sections that each answer a specific question. It’s a reason to structure long-form content carefully rather than writing in undifferentiated blocks.

The vocabulary in this field shifts faster than most. New terms emerge with each algorithm update, each tool release, and each shift in how Google communicates publicly. What matters is not memorising definitions but understanding which concepts carry commercial weight and which are mostly industry noise. In my experience, the practitioners who make the best decisions are the ones who can translate SEO terminology into business implications, not the ones who can recite the most definitions.

If you want to build a strategy around these concepts rather than just understand them in isolation, the Complete SEO Strategy hub covers how these terms connect into an integrated approach to organic search performance.

About the Author

Keith Lacy is a marketing strategist and former agency CEO with 20+ years of experience across agency leadership, performance marketing, and commercial strategy. He writes The Marketing Juice to cut through the noise and share what works.

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