What is Catastrophic forgetting?
Catastrophic forgetting is a training-stage concept in modern language models. It is part of the vocabulary teams use when they compare models, design prompts or review an AI system.
Definition
Catastrophic forgetting is a training-stage concept in modern language models. It is part of the vocabulary teams use when they compare models, design prompts or review an AI system. The term is used in training discussions, where precision matters: two teams can use the same word to mean slightly different things. In this glossary, catastrophic forgetting is treated as a practical concept rather than a formal specification.
Why it matters
Training terms cover how models learn from data, how preferences are shaped and how behaviour is adjusted after pre-training. They matter because most capability and safety differences are set during training, not at inference time.
Example
Suppose you are comparing Gemini 2.5 Pro with another model for a production task. Catastrophic forgetting is one of the factors behind the numbers you see: Gemini 2.5 Pro lists a 200,000-token context window, costs $15.20 per million input tokens and scores 1455.0 on Arena Elo. Understanding the term helps you decide which of those differences actually matter for your workload.
How to evaluate it
- Check whether catastrophic forgetting is defined the same way in the documentation you are reading.
- Ask which measurement or trade-off the term is describing before comparing numbers.
- Separate vendor claims from independently observed behaviour on your own data.
- Write down the definition your team uses so reviews and evaluations stay consistent.
Related terms
Related guides
FAQ
What does Catastrophic forgetting mean?
Catastrophic forgetting is a training-stage concept in modern language models. It is part of the vocabulary teams use when they compare models, design prompts or review an AI system.
Why does Catastrophic forgetting matter?
Training terms cover how models learn from data, how preferences are shaped and how behaviour is adjusted after pre-training. They matter because most capability and safety differences are set during training, not at inference time.
How is Catastrophic forgetting used in practice?
Suppose you are comparing Gemini 2.5 Pro with another model for a production task. Catastrophic forgetting is one of the factors behind the numbers you see: Gemini 2.5 Pro lists a 200,000-token context window, costs $15.20 per million input tokens and scores 1455.0 on Arena Elo. Understanding the term helps you decide which of those differences actually matter for your workload.