What words can mean both one who is served and to learn thoroughly 1.multitude 2.host 3.master 4.throng?

The word that can mean both "one who is served" and "to learn thoroughly" is 3. master.

Here's why:

* Master as a noun: Can refer to a person who is served, typically in a relationship of servitude or apprenticeship. Example: "The master commanded his servants."

* Master as a verb: Means to learn thoroughly or become proficient in something. Example: "She mastered the art of pottery."

The other words don't fit both meanings:

* Multitude, host, and throng all refer to a large number of people, not an individual served or the act of learning.