AI reference
Clear AI definitions and model data you can check.
A glossary written for practitioners, research summaries, and language models compared on price, limits and capabilities, with a source and a date next to every number.
Glossary
266 terms · A–Z
Definitions first, then how it works, worked examples, formulas and code.
LLM API pricing
62 models · 5 vendors
Per-token prices from each vendor's own page, with cache, batch and long-context rates.
Models
7 model cards · 6 comparisons
Context windows, limits and capabilities, with the source behind each value.
Tools
Token counter · cost calculator
Count the tokens in your prompt, then see what a month of traffic costs on every model.
LLM changelog
20 changes · last Sep 15, 2026
Model launches, price changes and retirements, each linked to the vendor's notice.
News and research
188 articles
Pricing news, research summaries and applied machine learning explainers.
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Fresh in the reference
Recently updated in the glossary
Latest articles
- Latest
LLM Hallucinations: Why They Happen and How to Reduce Them
Hallucination is the term for when a language model states something false with the same confidence it uses for something true. OpenAI's own research team put it…
Structured Outputs: How to Get Reliable JSON From an LLM
Structured outputs is the feature that stops an LLM's JSON from breaking your code. Instead of asking a model nicely to "please respond in JSON" and hoping, you hand it…
scikit-learn: The Machine Learning Library That Isn't Deep Learning
scikit-learn is a free, open-source machine learning library for Python — and, according to a 2022 Kaggle survey of nearly 24,000 developers across 173 countries, the…
TensorFlow: What It Is, Its Real History, and How to Use It
TensorFlow is Google's "end-to-end platform for machine learning" — its own description, not marketing gloss, since the project genuinely spans training, mobile and…
PyTorch: What It Is, Its Real History, and How to Use It
PyTorch is an open-source deep learning library originally built at Facebook AI Research (now Meta AI), and since September 2022 it's governed independently by the…
Claude Code Tutorial: From First Session to Subagents and Hooks
Claude Code is Anthropic's agentic coding tool: a terminal program, IDE extension, desktop app, and web client that reads your codebase, edits files, runs commands, and…