Main Entry: ad·den·dum

Pronunciation: \ə-ˈden-dəm\

Function: noun

Inflected Form(s): plural ad·den·da \-ˈden-də\ also ad·den·dums

Etymology: Latin, neuter of addendus, gerundive of addere

Date: 1684

1 : a thing added : addition
2 : a supplement to a book —often used in plural but singular in construction