noun

• (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).