verify
To check carefully that something is true or correct.
To verify means to check whether something is true or accurate. When you verify an answer on a math test, you work through the problem again to make sure you got it right. When a scientist verifies experimental results, she repeats the experiment to confirm the findings weren't just a lucky accident.
If your teacher asks you to verify your answer, she's asking you to show your work and demonstrate that your conclusion is correct. If a security guard verifies your identity, he checks your ID card to confirm you're really who you say you are.
Verification is the act of verifying something. Software engineers write tests for verification to ensure their code works correctly. Historians verify claims by checking multiple sources. Scientists insist on verification because they know that one experiment might be flawed or influenced by factors the researcher didn't notice.
When something is verifiable, it can be checked and proven. “I saw a UFO” is hard to verify. “Water freezes at 32 degrees Fahrenheit” is easily verifiable: anyone can repeat the experiment and see the same result.