The unit used to measure AI input and output for context window and API billing purposes. A token is roughly three-quarters of a word in English. A 1,000-word document is approximately 1,300–1,500 tokens. API pricing is based on tokens in (input) plus tokens out (output). Subscription plans don't charge per token but do impose usage limits tied to overall conversation length.
Token
Lessons that cover this
- What AI Actually IsA prediction machine, not a thinking one — and why that distinction explains almost everything else.
- What AI Actually CostsTwo pricing models, one crossover point, and the costs that never appear on the invoice.
- Tokens and the Context WindowThe two numbers behind every AI bill, every length limit, and every "it forgot what I said".
Related terms
This definition is part of a free, structured course on how AI actually works.
Start learning