Cause vs Source

When to use each in English, with meaning, register, and examples.

Cause

Top 1,000 (very common) A2 noun

Source

Top 1,000 (very common) A2 noun

	Cause	Source
Pronunciation	🇬🇧 /["/kɔːz/"]/ 🇺🇸 /["/kɔːz/"]/	🇬🇧 //sɔːs// 🇺🇸 //sɔrs//
Meaning	The reason something happens.	The place where something comes from.
Example	The cause of the accident was a flat tire.	The source of the river is located in the mountains.
Register	Neutral	Neutral
How common	Top 1,000 (very common)	Top 1,000 (very common)
CEFR level	A2	A2
Part of speech	noun	noun
Collocations	real, root, true, determine, discover, find, be, lie in something, remain, cause of, cause and effect, the cause of death, due to natural causes, good, great, real, have, find, give (somebody), cause for, cause for concern, with good cause, without good cause, deserving, good, just, advance, champion, embrace, for the cause of, in the cause of, in a/​the cause, (all) for a good cause, (all) in a good cause	source of information, primary source, data source
Antonyms	effect, result	destination, result
Common mistakes	Confusing 'cause' with 'because' in sentences., Using 'caused' incorrectly when the present form 'cause' is needed., Incorrectly using 'cause' as a noun instead of a verb.	Confused with 'resource' which refers to a supply or support., Used incorrectly as a verb; 'source' is only a noun in this context.
Usage notes	Use 'cause' in standard writing and conversation. In formal contexts, you might use 'cause' less frequently, opting for 'cause' instead. Avoid using it in very casual or children's language.	Used in both formal and informal contexts; can refer to information, origins, or places.

See it in real clips

The Pitt › S1 E1

It can cause heart problems.

Band Of Brothers › S1 E1

For whose cause?

Succession › S1 E1

"Cause it was raining and I didn't want to, um...

The Pitt › S1 E1

It can cause heart problems.

Band Of Brothers › S1 E1

For whose cause?

Cause

...but it's not the source.

Agents of S.H.I.E.L.D. › S1 E1

Every known source of superpower, thrown in a blender.

...but it's not the source.

Agents of S.H.I.E.L.D. › S1 E1

Every known source of superpower, thrown in a blender.

Source

Frequently asked questions: Cause vs Source

What's the difference between Cause and Source?

Cause: The reason something happens. Source: The place where something comes from.

Are Cause and Source the same CEFR level?

Cause: A2, Source: A2 on the CEFR scale.

What part of speech are Cause and Source?

Cause: noun, Source: noun.

Can you show an example of each?

Cause: The cause of the accident was a flat tire. Source: The source of the river is located in the mountains.

Can I use Cause and Source interchangeably?

Not always. Cause and Source are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.