(uncountable) The act of adding anything.

Anything that is added.

(uncountable) The arithmetic operation of adding.

(music) A dot at the right side of a note as an indication that its sound is to be lengthened one half.

(chiefly law) A title annexed to a person's name to identify him or her more precisely.

(heraldry) Something added to a coat of arms, as a mark of honour.

(organic chemistry) an organic reaction where two or more molecules combine to form a larger one (the adduct).