* What counts as a word? There's no single, universally accepted dictionary or list of all English words. Different dictionaries have varying criteria for what constitutes a "word." Some include proper nouns, slang, technical terms, etc., while others are more restrictive.
* Context matters: The meaning and validity of a three-letter word can depend on the context. For example, "the" is a valid word in a sentence but not a standalone word.
* New words are constantly created: The English language is dynamic. New words emerge, and old ones fall out of use.
However, here's some information to help you estimate:
* Common three-letter words: There are definitely hundreds of common three-letter words in the English language. Think of words like "and," "but," "the," "see," "run," etc.
* Word lists: You can find lists of common words online, some of which might focus on three-letter words.
Rather than searching for an exact number, focusing on the common three-letter words will likely be more helpful for most purposes.