You're Not Reading Words, You're Reading Chunks: Tokens and Context Windows Explained.

AI models don't read words — they read subword chunks called tokens. Every model also has a context window: a hard limit on how much text it can hold in attention at once. Understanding both changes how you write prompts, how you estimate costs, and why AI occasionally behaves in ways that otherwise seem inexplicable. This is Part 2 of a five-part series from the Vectors pillar of Context First AI. Built for anyone starting their AI journey — developer or not. No prior knowledge assumed beyond Part 1. Full series: Part 1 — The Autocomplete That Ate the World* Part 2 — You're Not Reading Words, You're Reading Chunks* Part 3 — Meaning Has a Shape* Part 4 — You're Not Writing Prompts, You're Writing Instructions for a Very Particular Mind* Part 5 — What to Do When the Model Doesn't Know Enough The Session That Went Wrong It started during a long research session — a product team working through a complex competitive analysis with an AI assistant, building up context across dozens of excha