Confusingly, what was once called a coat is now commonly referred to
as a
jacket, as in a
dinner jacket, although the original meaning is still used in
tailoringto mean the upper part of a
suit, for example.
What is now
commonly called a coat
an outer layer of clothing such as a
trench coat
is, in tailoring terms,
correctly called an
overcoat, since it is worn over the
coat.