Word count is the number of words in a piece of text. The most common definition counts every whitespace-separated token, so numbers, hyphenated compounds, and contractions each count as a single word. Under this rule the sentence "I'll meet you at 3 o'clock — bring 5 well-thumbed books" counts as 11 words: I'll, 3, o'clock, and well-thumbed are one word apiece. Most word processors (Microsoft Word, Google Docs) and academic counters follow this convention, which is also what our Word Counter reports.
Where is word count used? Academic assignments and journal submissions impose strict limits (an essay capped at 2,000 words, an abstract at 250). Freelance writers and journalists are frequently paid per word, so an accurate count is a billing figure. SEO teams target rough length bands for pages, and social platforms enforce hard ceilings. Because the count feeds all of these, small definitional differences matter.
Specialised contexts diverge from the whitespace rule. Some legal counters split hyphenated compounds into two words; some translation tools exclude standalone numbers; a few copywriting tools drop very short stop words. The mechanics come down to tokenization — how the text is split before anything is counted — which is also why two tools can disagree on the same paragraph. A common misconception is that word count equals reading time; that depends on reading speed and content difficulty. When a limit is binding, count with the same convention your destination platform uses, and check character count too if the platform limits characters instead.