AI

Token

The unit an LLM reads and writes in — a chunk of text, roughly three-quarters of a word.

LLMs don't see letters or whole words; they see tokens, which are common character sequences. 'Hamburger' might be one token, while a rare word like 'antidisestablishmentarianism' is several. This matters for two very practical reasons: you're billed per token (both input and output), and every model has a hard token limit. Rough rule of thumb: 1,000 tokens is about 750 English words.