The verb examine means to study something carefully and in great detail. You can examine a book, a painting, a person’s face and so on. Right now, you are examining the meaning of examine.
Examine means to look at something very closely and usually with the purpose of making a judgment. If you go to see a doctor, the doctor will examine you to see if you are healthy. Examine can also mean “question.” When the police examine a witness, they are questioning that witness. Along these same lines, examine can also be used to mean “test.” You might examine, or test, your friend’s knowledge of biology by asking him repeated questions about that subject.