Capable of being put into one-to-one correspondence with the positive integers; countable.
The empty set is denumerable because it is finite; the rational numbers are, surprisingly, denumerable because every possible fraction can be assigned a number.
Origin of denumerable
- From denumerate to count from Late Latin dēnumerāre dēnumerāt- alteration of Latin dīnumerāre dī-, dis- dis- numerāre to number numerate
From American Heritage Dictionary of the English Language, 5th Edition