What was that vs What was what

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

What was that

Top 2,000 (common)

What was what

Beyond 10,000 (less common)
Most common: What was that
 What was thatWhat was what
Pronunciation🇬🇧 //wɒt wəz ðæt//🇺🇸 //wɑt wəz ðæt//🇬🇧 //wɒt wəz wɒt//🇺🇸 //wɑt wəz wɑt//
MeaningA question asking for clarification about something that happened.A phrase used to clarify or question something previously mentioned.
ExampleDid you hear that? What was that?I didn't understand the project details. What was what?
RegisterNeutralNeutral
How commonTop 2,000 (common)Beyond 10,000 (less common)
Collocationswhat was that noise, what was that sound, what was that aboutexplain what was what, understand what was what, clarify what was what
AntonymsI understand, That is clear-
Common mistakesConfused with 'what is that?' which asks about something present., Used in formal situations where clarity is important., Overused in conversations, when direct questions could suffice.Using it in overly formal contexts, Confusing it with 'what is what', Not using it to emphasize confusion or clarity
Usage notesUse when you need to clarify something you didn't hear or understand. Avoid in formal presentations.Use this phrase when seeking clarification or repeating a previous point. It is commonly informal and can be used in discussions or conversations.

See it in real clips

What was that
What was what

Frequently asked questions: What was that vs What was what

What's the difference between What was that and What was what?

What was that: A question asking for clarification about something that happened. What was what: A phrase used to clarify or question something previously mentioned.

Which is more common: What was that and What was what?

What was that is the most common in everyday English.

Can you show an example of each?

What was that: Did you hear that? What was that? What was what: I didn't understand the project details. What was what?

Can I use What was that and What was what interchangeably?

Not always. What was that and What was what 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.

Related comparisons