Two statements in logic are said to be equipollent if they
are deducible from each other.
Two sets
and are said to be equipollent iff
there is a one-to-one correspondence (i.e., a bijection)
from onto (Moore 1982, p. 10; Rubin 1967, p. 67; Suppes 1972,
p. 91).
The term equipotent is sometimes used instead of equipollent.
and 
are said to be equipollent iff
there is a one-to-one correspondence (i.e., a bijection)
from 
onto 
(Moore 1982, p. 10; Rubin 1967, p. 67; Suppes 1972,
p. 91).
