Definition
Plain language
OpenAI's family of large language models, including the 4 and 5 series.
As stated in the literature
OpenAI's foundation model series including GPT-4, GPT-4o, GPT-4 Turbo, and the GPT-5 family, including reasoning variants.
Also called: GPT-4o, GPT-4 Turbo, GPT-4o-mini, GPT-4.1, GPT-5, GPT-5-mini, GPT-5-nano, GPT-5.1, GPT-5.2, GPT-5.2R, GPT-5.4, GPT-5.5
Why it matters: It set the expectations and pricing for the current generation of frontier chatbots, and successor models are still measured against it.
For example, GPT-4 was the model that popularized using ChatGPT for serious coding and writing tasks.
Heard on the show
“Take o3-mini, OpenAI's reasoning-specialized model, and GPT-4o-mini, its ordinary sibling.”Episode 197 — Twin Problems Suggest AI Reasoning Gains Are Mostly Better Fact Recall