How can you tell it's a suit jacket?
1. The tag not only has the jacket size, but also the waist size of the pants. 2. The material combined with the pattern: this weave is much smoother than most sport coats, which typically (not always, and excepting the fabric of some solid-color sportcoats) are of a more open and/or coarser appearing
weave, and the pattern, which is a small scale plaid, which you rarely see in a sportcoat, and certainly not in this type of fabric. Typically, sport coats have larger patterns, since they will be paired with solid color trousers, or more tweed-like fabrics. The large pattern of sportcoats would look, to many tastes, overwhelming in a suit -- the exception to this assertion is the "country suit" beloved of the British and certain anglophiles. The notion of wearing a suit jacket as a sport coat has been discussed before. Some like it, feeling it gives off an air of nonchalance and casualness, while others (including me) think it looks like the wearer bought the jacket at a thrift store.