/TOH-kun/
The basic unit of text that AI models process — roughly 3/4 of a word. Tokens determine cost, context limits, and processing speed.
A token is how AI models see text. Rather than reading word by word, models break text into tokens — fragments that are roughly 3/4 of a word on average. 'Unbelievable' might be three tokens: 'Un', 'believ', 'able'. Common words like 'the' are usually one token. This matters because everything in AI is priced and limited by tokens.
Context windows are measured in tokens (Claude has 200K, GPT-4 has 128K). API pricing is per-token. Response speed depends on tokens generated. When someone says 'I ran out of context,' they mean they hit the token limit.
Understanding tokens gives you practical superpowers: you can estimate costs, know when to summarize instead of dumping full documents, and understand why some prompts work better than others (shorter prompts leave more room for the response).
When discussing AI costs, context limits, prompt optimization, or debugging why a long conversation started losing quality.
Token literacy is financial literacy for AI. Every wasted token costs money and displaces useful context.
Think of arcade tokens — you have a limited number, each one lets you play a little more, and when they're gone, the game's over.
A Mac app that coaches your AI vocabulary daily