Synonyms for add include to increase
by adjoining or uniting: in distinction from multiply, which is to increase by repeating.
To augment a thing is to increase it by any means, but this word is seldom used directly of material
objects; we do not augment a house, a farm, a nation, etc.
We may enlarge a house, a farm, or an empire, extend influence or dominion, augment riches,
power or influence, attach or annex a building to one that it adjoins or papers to the
document they refer to.
We can annex a clause or a codicil, affix a
seal or a signature, annex a territory, attach a condition to a promise.
A speaker may amplify a discourse by a fuller treatment throughout than was originally planned, or he may
append or subjoin certain remarks without change of what has gone before.
We cast up or sum up an account, though add up and make up are now more usual