Looking up an unfamiliar word usually means copying it, opening a new tab and searching, which breaks your reading flow. A dictionary extension shortcuts this by showing a definition directly on the page you are reading, triggered by double-clicking the word or selecting it and clicking a small icon.
Double-click definitions while reading
The core feature to check is how the definition appears: most dictionary extensions show a compact popup near the word when you double-click it, so you never leave the page. Some also support looking up a full selected phrase, not just a single word, which helps with idioms and technical terms.
Pronunciation and translation features
Beyond definitions, many dictionary extensions add audio pronunciation and a translation option for looking up the same word in another language. If you read in more than one language, check that the extension supports language pairs you actually need before relying on it.
When a browser dictionary isn't enough
A quick popup definition suits everyday reading, but it won't replace a full dictionary app for etymology, multiple detailed senses or a thesaurus with synonyms. For deeper research, use the extension for a fast first look, then switch to a dedicated dictionary site when you need more detail.