Many verbs in English are followed by an adverb or a preposition (also called a particle), and these two-part verbs, also called phrasal verbs, are different from verbs with helpers. The particle that follows the verb changes the meaning of the phrasal verb in idiomatic ways:
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.
Some particles can be separated from the verb so that a noun or pronoun can be inserted, and some particles can't be separated from the verb
