mat·ter 
(mătər)
(mătər)n.
1. That which occupies space and has mass; physical substance.
2. A type of such substance: organic matter.
3. Discharge or waste, such as pus or feces, from a living organism.
4. Philosophy In Aristotelian and Scholastic use, that which is in itself undifferentiated and formless and which, as the subject of change and development, receives form and becomes substance.
5. The substance of thought or expression as opposed to the manner in which it is stated or conveyed.
6. A subject of concern, feeling, or action: matters of foreign policy; a personal matter. See Synonyms at subject.
7. Trouble or difficulty: What's the matter with your car?
8. An approximated quantity, amount, or extent: The construction will last a matter of years.
9. Something printed or otherwise set down in writing: reading matter.
intr.v. mat·tered, mat·ter·ing, mat·ters
Idioms: To be of importance: "Love is most nearly itself / When here and now cease to matter" (T.S. Eliot).
as a matter of fact
In fact; actually.
for that matter
So far as that is concerned; as for that.
no matter
Regardless of: "Yet there isn't a train I wouldn't take, / No matter where it's going" (Edna St. Vincent Millay).
[Middle English mater, from Old French matere, from Latin māteria, wood, timber, matter, from māter, mother (because the woody part was seen as the source of growth); see māter- in the Appendix of Indo-European roots.]