phrasal verb

http://owl.english.purdue.edu/owl/resource/630/01/
(phrasal verb)

• drop off - decline gradually

  The hill dropped off near the river

• drop off(2) - fall asleep

  While doing his homework, he dropped off.

• drop off(3) - stop and give something to someone

  Would you drop this off at the post office?

• drop out - cease to participate

  After two laps, the runner dropped out.

• Separable
  add up (meaning: to add)

  Correct: She added up the total on her calculator.
  Incorrect: She added it up on her calculator.

• Inseparable
  get around (meaning: to evade)

  Correct: She always gets around the rules.
  Incorrect: She always gets the rules around (This construction makes no sense in English.)

• Intransitive
  catch on (meaning: to understand)

  Correct: After I explained the math problem, she began to catch on.
  Incorrect: She began to catch on the math problem. (catch on cannot take a direct object in this meaning.)
  Correct: She began to catch on to the math problem. (the word to makes the math problem an indirect object, which is acceptable in this meaning.)