Q:

Do phrasal verbs depend on understanding English?

I was wondering if phrasal verbs depend on understanding English.
Do native speakers just memorize phrasal verbs they've been hearing over their lives, or they can create new phrasal verbs while talking because they understand English well?

A:

Phrasal verbs are associated with idiomatic expressions. They are the "verb" part of a "phrase", and that phrase is usually an idiomatic expression. An idiom, by definition, takes on a meaning different from the words making up the idiom. So, no, we don't make up new idioms on the spot. The listener would not understand what's meant. The phrase (the idiom) needs to simply be learned.
For example, when a car "breaks down," it is not literally moving "down" and it did not visibly split into pieces (break). That phrase is an idiom meaning that the car no longer functions as a car should. It's no longer able to travel. The "break down" might be due to a flat tire, or might be due to the cylinder head gasket. Either way, the car doesn't run; it can't travel.

