To grasp the meaning, significance, or nature of something. I understand the instructions you gave me.
To perceive the intended meaning of words, a language, or a speaker. She can understand French but doesn't speak it fluently.
To infer something from information received. From his tone, I understand that he is upset.
To interpret or view something in a particular way. I understand his actions as a sign of goodwill.
To be sympathetically or knowledgeably aware of someone's feelings or situation. He always tries to understand his younger brother's problems.
To learn or be told something and accept it as true. I understand that the meeting has been postponed.