[uh-den-duh
m] 
[-duh] for 1, 2; -dums for 3. | 1. | a thing to be added; an addition. |
| 2. | an appendix to a book. |
| 3. | Machinery.
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| ad·den·dum (ə-děn'dəm) n. pl. ad·den·da (-də) Something added or to be added, especially a supplement to a book. [Latin, neuter gerundive of addere, to add; see add.] |