ModelRefs / Chain of Thought (CoT) — AI Glossary

Chain of Thought (CoT) — AI Glossary

A prompting technique that asks a model to reason step-by-step before producing a final answer. 'Let's think step by step' is the minimal CoT trigger.

Overview

Chain-of-thought (Wei et al., 2022) substantially improves accuracy on math and multi-step reasoning tasks. 'Let's think step by step' is the minimal CoT trigger. Modern reasoning models (o1, o3, R1) build CoT into the model via RL on verifiable rewards rather than relying on the prompt.

Reference details

Topic	reasoning
Also known as	CoT, chain of thought prompting
Last reviewed	2026-06-24

Example: Where the reasoning has to go

“A train leaves at 14:20 and takes 3h50m; the connection departs 15 minutes after arrival. When?” Answered directly, models often slip on the hour boundary. Asked to work through it — 14:20 + 3h50m = 18:10, plus 15 minutes = 18:25 — the intermediate step is written down, so the arithmetic is done rather than recalled, and a wrong step is visible instead of hidden.

Commonly confused with

The visible chain is not necessarily the computation. Models can produce a correct-looking rationale for a wrong answer, and a plausible rationale for a right one reached another way. Chain-of-thought improves accuracy on multi-step problems; it is not an explanation of what the network did.

When to use it

Reach for it when:

The task genuinely has intermediate steps: arithmetic, multi-hop, planning
You want a wrong step to be inspectable rather than buried
The model is not already a reasoning model with this built in

Reach for something else when:

Single-step lookup or classification, where it costs tokens and adds nothing
Latency-critical paths — reasoning tokens are generated before any answer appears
On reasoning models trained to reason internally; prompting for it can interfere

Primary source

Wei et al., Chain-of-Thought Prompting Elicits Reasoning in Large Language Models (arXiv)

Referenced by

This term is used by the following ModelRefs references:

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Frequently asked questions

What is Chain of Thought (CoT)?

A prompting technique that asks a model to reason step-by-step before producing a final answer.

Is Chain of Thought (CoT) the same as CoT?

Yes — CoT, chain of thought prompting are common aliases for Chain of Thought (CoT).

What concepts are related to Chain of Thought (CoT)?

Closely related concepts include zero shot, few shot, reasoning model, self consistency.