In
logic, statements <var>p</var> and <var>q</var> are
logically equivalent if they have the same logical content. This is a
semantic concept; two statements are equivalent if they have the same
truth value in every
model (Mendelson 1979:56). The logical equivalence of <var>p</var> and <var>q</var> is sometimes expressed as , E
pq, or . However, these symbols are also used for
material equivalence; the proper interpretation depends on the context. Logical equivalence is different from material equivalence, although the two concepts are closely related.