https://www.merriam-webster.com/dictionary/matter
Definition of matter
1
a : a subject under consideration Several other matters will come before the committee. 
b : a subject of disagreement or litigation The matter in dispute is basically trivial. 
c matters plural : the events or circumstances of a particular situation planned to discuss matters with her husband soon 
d : the subject or substance of a discourse or writing A graceful style was not enough to hide a paucity of matter. 
e : something of an indicated kind or having to do with an indicated field or situation this is a serious matter as a matter of policy matters of faith 
f : something to be proved in law 
g obsolete : sensible or serious material as distinguished from nonsense or drollery 
h (1) obsolete : reason, cause (2) : a source especially of feeling or emotion 
i : problem, difficulty What's the matter? 
2
a : the substance of which a physical object is composed 
b : material substance that occupies space, has mass, and is composed predominantly of atoms consisting of protons, neutrons, and electrons, that constitutes the observable universe, and that is interconvertible with energy 
c : a material substance of a particular kind or for a particular purpose vegetable matter 
d (1) : material (such as feces or urine) discharged from the living body (2) : material discharged by suppuration : pus 
3
a : the indeterminate subject of reality; especially : the element in the universe that undergoes formation and alteration 
b : the formless substratum of all things which exists only potentially and upon which form acts to produce realities 
4
: a more or less definite amount or quantity cooks in a matter of minutes 
5
: something written or printed matter suitable for photocomposition 
6
: mail first-class matter 
7
Christian Science : the illusion that the objects perceived by the physical senses have the reality of substance