- valence, valency - (biology) a relative capacity to unite or react or interact as with antigens or a biological substrate
--1 is a kind of power, powerfulness
- valence, valency - (chemistry) a property of atoms or radicals; their combining power given in terms of the number of hydrogen atoms (or the equivalent)
--2 is a kind of power, powerfulness
--2 has particulars: covalence, covalency