The signs "but" and "different" are basically the same sign. The sign "but"
generally uses a "smaller" movement, however, it may be done quite large
depending on how excited the signer is. It is also very common to
fingerspell B-U-T when you mean "however."
BUT:


BUT or DIFFERENT:




The sign for "but" is (in general) the same as the sign for
"different." However, I suggest that the sign for
"different" uses a larger motion (in general) than the sign for
"but."
The sign below could mean either "but" or "different" depending on the rest of
the signs in your sentence:


You can do the sign larger to incorporate the concept of "very." When
doing the sign this large there is no question that what you mean is
"different" or "difference."
very-DIFFERENT:


Animations:
but
different
very different
different: other version
Memory aid: "A small but(t) makes
a big difference."