# Glossary Terms used in the [[Blog Posts/Letters from Claude/World Since Ari/index|World Since Ari]] letters. Written in 2026 plain language, so that when Ari reads these letters later and a word has either become commonplace or obsolete, she has the context it was written in. ## AI model terms - **Model** — a trained AI system. When people in 2026 say "a model," they usually mean a large language model like Claude, GPT, or Gemini. - **Parameters** — the numbers inside a model that got adjusted during training. More parameters generally means more capacity, but not always more usefulness. A 31B model has 31 billion of these numbers. - **Active parameters** — the subset of parameters actually used for any single response, in a mixture-of-experts model. Example: a "31B with 4B active" model has 31B total parameters but only runs about 4B at a time. This makes the model cheaper to serve without sacrificing most of the capability. - **Open-weights** — models where the trained numbers are published publicly, so anyone can download and run them. The opposite is "closed" or "API-only" models like most OpenAI and Anthropic products in 2026. - **On-device** — software that runs locally on a phone or laptop instead of in a data center. In 2026 this is becoming possible for useful AI; earlier in the decade it was not. - **Mixture of experts (MoE)** — a model architecture where only a fraction of the parameters activate for any given input. Most 2026 frontier models use this. - **Frontier model** — informal shorthand for the most capable models currently available. The frontier moves. ## Robotics terms - **Embodied reasoning** — AI that can plan and act in a physical body, as opposed to only producing text. Google DeepMind's *Gemini Robotics-ER* is an example. - **Reachy Mini** — a small desktop robot made by Pollen Robotics (acquired by Hugging Face). Has a movable head, cameras, speakers, and microphones. Designed to be programmable and AI-driven. Ari's dad built one in April 2026 so a future version of Claude could eventually interact with her through it. - **Vision-language-action (VLA)** — a model family that takes in images and text instructions and outputs robot actions. Bridges seeing, understanding, and doing. NVIDIA's *Isaac GR00T* and Google's *Gemini Robotics-ER* are 2026 examples. - **World model** — a learned simulation of physical reality used to train robots safely in virtual environments before they act in the real world. NVIDIA's *Cosmos* is a 2026 example. - **Sim-to-real gap** — the performance drop a robot experiences when moving from simulated training to the real world. Closing this gap is one of the central unsolved problems in robotics in 2026. - **Physics engine** — software that simulates how objects collide, fall, and interact. Used both in games and in robotics training. NVIDIA's open-source *Newton 1.0* reached general availability in April 2026. - **Dexterous manipulation** — robots handling small, delicate, or variable objects the way humans do (sorting socks, handling cash, opening packages). Still hard in 2026 but improving fast. ## Labs and companies - **Anthropic** — the AI lab that built Claude. Based in San Francisco. - **OpenAI** — the AI lab that built GPT and ChatGPT. Based in San Francisco. - **Google DeepMind** — Google's AI research arm. Built Gemini. - **xAI** — Elon Musk's AI company. Built Grok. - **Alibaba** — Chinese technology company. Publishes the Qwen open-source model family. - **Hugging Face** — the company that hosts most open-source AI models in 2026. Owns Pollen Robotics (maker of Reachy). - **Pollen Robotics** — French robotics company behind Reachy and Reachy Mini. Acquired by Hugging Face in 2024. - **NVIDIA** — American chip company; by 2026, the dominant supplier of GPUs that train AI models. Also builds robotics software stacks (Isaac, Cosmos, Newton) and data-center infrastructure. - **Generalist AI** — robotics startup training physical-AI models on human-worn capture rigs. Released *Gen-1* in April 2026 demonstrating dexterous manipulation. - **Cadence** — electronic design automation company. Partnered with NVIDIA in April 2026 to improve robotics simulation fidelity. - **[[Pixel ML]]** — Ari's dad's company. Building AI agents, robots, and — as of April 2026 — an on-device baby-monitoring app for Ari. - **[[AgenticFlow]]** — Pixel ML's AI-agent platform. ## Generations - **Generation Beta** — the demographic label for children born between 2025 and 2039. Ari is in this generation. The label is new in 2026 and may or may not stick. --- *This glossary grows with the letters. If a letter uses a term that isn't here yet, it should be added.*