AI Term

What is Token?

A unit of text that AI language models process—roughly equivalent to about 4 characters or 0.75 words in English. Tokens determine context limits and pricing.

In the context of AI language models, a token is a unit of text that the model processes. Understanding tokens is essential for working with AI effectively and managing costs.

What Is a Token?

A token is roughly:

  • 4 characters of English text
  • About 0.75 words
  • Sometimes a whole word, sometimes a part of a word

    • The word "hamburger" might become two tokens: "ham" and "burger"

    The phrase "I love AI" is 3 tokens

    Why Tokens Matter

    Context Windows

    Every AI model has a maximum number of tokens it can process at once. This includes both your input and the model's output.

    | Model | Context Window |

    |-------|---------------|

    | GPT-3.5 | 16K tokens (~12,000 words) |

    | GPT-4 | 128K tokens (~96,000 words) |

    | Claude | 200K tokens (~150,000 words) |

    Pricing

    API usage is typically charged per token. Both input and output tokens count toward your bill.

    Response Limits

    Longer prompts leave less room for responses. A very long input may result in truncated outputs.

    Token Counting

    Different models tokenize text differently. A sentence that's 20 tokens in GPT-4 might be 22 tokens in another model.

    Tools exist to count tokens before sending to an API, helping you stay within limits and estimate costs.

    Practical Implications

    For Users

  • Very long conversations may hit limits
  • Complex prompts consume tokens from response capacity
  • Including unnecessary context wastes tokens

    • For Developers

  • Token limits affect application design
  • Costs scale with token usage
  • Efficient prompting saves money

    • Tips

  • Be concise without sacrificing clarity
  • Remove redundant examples and context
  • Use summaries instead of full documents when possible
  • Monitor token usage for cost management

    • Examples

    Context window limitsAPI pricingMessage length limits

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    Related Terms

    ChatGPT

    An AI chatbot created by OpenAI that can understand and generate human-like text, answer questions, write content, and assist with various tasks through conversation.

    Prompt Engineering

    The practice of designing and optimizing inputs (prompts) for AI systems to get the most accurate, useful, and relevant outputs.

    Large Language Model (LLM)

    An AI model trained on massive amounts of text data that can understand, generate, and work with human language at a sophisticated level.