Definitions of understand:

• verb:   know and comprehend the nature or meaning of

  Example: "She did not understand her husband"

• verb:   perceive (an idea or situation) mentally

  Example: "I don't understand the idea"

• verb:   believe to be the case

  Example: "I understand you have no previous experience?"

• verb:   make sense of a language

  Example: "She understands French"

• verb:   be understanding of

  Example: "You don't need to explain--I understand!"