back up (2)

Meaning: If you back up what you say, you use evidence or examples to show that it's true.

Synonym: support

For example:

back sth up When making a claim, you should be able to use evidence to back it up.
back up sth They'll back up her story with photos, video clips and witness statements to prove that what she's saying is true.
back sth up with sth When writing an essay, you should state your main idea and then back it up with supporting evidence.

Nouns often used as objects with
back up (2): claim, thesis, hypothesis, belief, contention, idea
back up with: evidence, examples, proof

Quick Quiz:

If you accuse someone of doing something wrong, make sure you can back up what you say with

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