An examination is a formal test that measures what you know or can do. When your teacher gives you a math examination at the end of the semester, she's checking whether you've learned the material. Doctors perform physical examinations to assess your health. Scientists conduct examinations of rock samples to understand what they're made of.

The word suggests something more thorough and official than a quick quiz. An examination takes time and covers material systematically. A detective's examination of a crime scene means carefully looking at every detail. When a jeweler examines a diamond, she studies it closely under special lights and magnifying tools.

You might also hear people say they're under examination, meaning others are looking closely at their work or behavior.

The verb form is examine. When you examine something, you inspect it carefully and thoughtfully, whether that's a mysterious bug you found outside or the arguments in a debate.