There are three levels of coat, and we use the term coat here to define it as the overall style of stiff torso fabric with sleeves meant to be worn over a dress shirt. They go in ascending order from casual to formal, and their material, design and function follow this progression. They are the sport coat, the blazer, and the suit jacket. There is a certain level of confusion as to which coat is meant for which occasion. In general if the more casual the event the better the sport coat. The more restrained yet not quite formal, then the blazer. The more formal or the completely formal, then the suit jacket, and finally, though not within the discussion here, we have the height of modern formality, the tuxedo jacket. Let us discuss each coat in turn.
The Sport Coat
Made from sturdier materials, the sport coat is descended from the hunting tweed coat meant for outdoor activity. When compared with the blazer and suit jacket the sport coat immediately gives off a feeling of casualness and ease. Sport coats often carry flashy colors and designs. Sport coats can come with or without elbow patches and many have flap pockets. Sport coats go well with tweed, khaki and denim but are off putting when paired with dress slacks of similar color.
Blazers are in the middle range between sport coats and suit jackets. They are sharper than sport coats, but not as formal as suit jackets. The traditional fabric of the blazer is wool and the color is a standard blue. The buttons on a blazer are traditionally silver or gold. These traditions have weakened overtime and many designers have created blazers in a variety of color and fabrics. However within public consciousness blue is still the proper style of the blazer. Blazers often come with patch pockets and these may also have flaps.
The Suit Jacket
The suit jacket is made from finer wool, cotton or linen. A suit jacket must come with dress slacks of the same color and material. In sartorial parlance, a suit jacket without matching slacks does not exist. A suit jacket’s fabric must be delicate in comparison to the sport coat and blazer. It is not intended for casual gatherings or outdoor activity. The suit jacket is a formal affair, with formal in the modern regard meaning a business setting. The three main styles of suit jacket are American, English and Italian. Suit jackets may also have flap pockets but in contemporary style jetted pockets are often preferred.