from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The number of arguments or operands a function or operation takes. For a relation, the number of domains in the corresponding Cartesian product.
- n. Valence.
from The Century Dictionary and Cyclopedia
- n. In chem., combining capacity, according as an element or a compound is a monad, dyad, etc.; same as valency.
From Ancient Greek root -ad, + -icity. Compare arity, which comes from the corresponding Latin root. (Wiktionary)