Token
A chunk of text or data that a model reads or writes while processing a prompt or response.
Plain English
Models do not read whole words exactly the way people do; they work in smaller pieces called tokens.
Example
A short sentence may become a dozen tokens, and both input and output tokens usually count toward cost.
Why it matters
Tokens affect context limits, pricing, latency, truncation, and how much information can fit in a request.
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