What Is Define on Select? How In-Page Dictionary Lookups Help You Read Unfamiliar Words

Reading a sentence and hitting a word you don’t quite know is one of the most common small interruptions in reading online. The usual response is either to guess at the meaning from context and keep going, or to stop, open a new tab, search the word, read the result, and then scroll back to find the sentence you were on. Neither is great: guessing risks misunderstanding the point of the sentence, and looking it up properly costs enough effort that most people skip it more often than they’d like to admit. An in-page dictionary lookup is a small feature aimed at removing that trade-off entirely.

The real cost of leaving the page for a definition

Opening a new tab to look up a word doesn’t just cost the few seconds a search takes. It also costs your place in the article, the thread of the sentence you were mid-way through, and whatever attention you’d built up reading to that point. For dense or long-form reading, that kind of context switch is exactly the sort of interruption that makes finishing an article harder than it needs to be — the same problem covered in reading strategies for ADHD, where losing your place mid-paragraph is one of the biggest barriers to getting through a page at all.

Even a “quick” lookup adds up. If a page has several unfamiliar words — common in academic writing, legal or medical text, or anything written for a specialist audience — repeating that new-tab-and-back cycle for each one turns a single article into a dozen small detours. In practice, this is usually why people just skip the lookup and guess instead, which quietly erodes how much of the article they actually understood.

Why context matters for learning a word, not just understanding a sentence

There’s a difference between looking up a word to get through one sentence and actually learning it well enough to recognize it next time. Vocabulary research generally favors encountering a word in the sentence it naturally appears in over memorizing it from an isolated list, because the surrounding context gives you extra cues — how the word is used, what part of speech it is, what kind of idea it’s attached to — that a bare definition on a flashcard doesn’t provide. A lookup tool that keeps you on the page, right next to the sentence the word came from, preserves exactly that context instead of stripping it away the way a separate search tab does.

Who this matters most for

Anyone can hit an unfamiliar word, but a few groups run into it more often, and benefit more from removing the friction of looking it up:

• Language learners. Reading in a second language means encountering unfamiliar vocabulary far more often than a native reader would, and the new-tab-and-back cycle becomes a constant interruption rather than an occasional one.
• Students and researchers working through technical or academic text. Dense material — scientific papers, legal documents, unfamiliar subject-matter writing — tends to cluster specialized vocabulary in ways that make repeated lookups routine rather than rare.
• Readers with dyslexia or attention difficulties, for whom breaking reading flow to search elsewhere costs more focus to recover from than it does for other readers. The best fonts for dyslexia guide covers other formatting choices that reduce this kind of friction.
• Anyone reading unfamiliar jargon casually — a news article that drops an economics or medical term without defining it, for instance — where stopping to open a search engine feels like too much effort for one word, so the word just gets skipped.

What a good in-page dictionary should actually show

Not all “quick lookup” tools are equally useful. A definition that’s genuinely helpful needs a few specific pieces, not just a one-line guess:

• A real definition, sourced from an actual dictionary rather than inferred from surrounding text.
• Part of speech, since the same word can mean different things as a noun versus a verb, and knowing which one applies to the sentence you’re reading matters.
• Pronunciation, useful for building a mental model of the word beyond just its written meaning, especially for language learners.
• An example sentence, when available, which reinforces the context point above by showing the word used naturally rather than only defined abstractly.

How ReadEase’s Define on Select works

ReadEase’s Define on Select feature, in the Dictionary panel, adds exactly this kind of lookup directly on the page. Select or double-click a single word and a small popover appears right next to it, showing the word, its part of speech, pronunciation, definition, and an example sentence when one is available — no new tab, no losing your place in the article.

A few details worth knowing:

• It’s built for single words, not phrases or full selections — it’s meant for the specific “what does this word mean” moment, not as a general search tool.
• Definitions come from a real dictionary source by default, so results are actual dictionary entries rather than a best guess at meaning.
• Words the default dictionary doesn’t have — less common terms, slang, or newer words — can optionally fall back to your own free-tier AI API key, if you choose to add one, so obscure words aren’t simply reported as “not found.”
• It only activates when you turn it on, so it stays out of the way entirely if you’d rather select text for other reasons, like copying it or highlighting a passage.

Trying it

1. Install ReadEase, a free Chrome extension.
2. Open the extension popup and turn on the Dictionary panel.
3. Toggle on Define on Select.
4. On any page, double-click or select a single unfamiliar word.
5. A popover appears next to the word with its definition, part of speech, and pronunciation — click elsewhere or scroll to dismiss it.

Because it works on the page you’re already reading, it’s worth trying on something you’d normally skim past a hard word in — a technical article, a piece written for a different audience than you, or anything in a second language you’re still building vocabulary in — to see how much of a difference not losing your place actually makes.

Frequently asked questions

Does Define on Select work on phrases or full sentences?

No — it’s built for single-word selections. Selecting more than one word or a full phrase won’t trigger a lookup, since the feature is aimed specifically at unfamiliar individual words rather than general search.

Is this the same as my browser’s built-in “look up” or “search” feature?

Not quite. Most browsers and operating systems offer some version of a right-click “search” or “look up” option, but these often open a new tab or a separate search results page rather than showing the definition inline, which reintroduces the same context-switching cost an in-page popover is meant to avoid.

Where do the definitions come from?

By default, Define on Select uses a free dictionary data source for common English words. If a word isn’t found there, it can optionally fall back to an AI-based lookup using your own API key, which you can add or leave unset entirely.

Will this slow down normal reading or text selection?

No — it only activates on single-word selections when the feature is turned on, so selecting text for other purposes, like copying a passage or using another ReadEase feature, isn’t affected.