matter

A matter is something that you can talk about or do something about a topic or a situation.

Example: Government must make these changes as a matter of urgency.

Matter is the stuff that everything is made of.

Example: Cities are trying to separate organic matter and other garbage.

You use, "as a matter of fact" to add information that may be surprising.

Example: "Have you met anyone interesting over there?" "As a matter of fact, I met a whole bunch of people just this afternoon.

You use "what's the matter" to ask somebody why they are unhappy, or why there is a problem.

You use "for that matter" when you have just thought about something that you are comparing to something else.

Example: He wasn't very nice today. For that matter, he's never nice.