Sports jackets. Suit jackets. Blazers. Most men use these terms interchangeably, as do many men’s clothing stores. Hopefully this information once and for all sort out the differences between these three jacket types.

BLAZER

Dressier than a sport coat, but more casual than a suit jacket. Blazers have a looser fit compared to suit jackets.
Originally worn by members of boating clubs
Usually solid in color, most commonly in navy and black
Traditionally made from wool, the most common fabrics used include blue worsted serge, flannel and hopsack.
Another detail that sets blazers apart from the suit jacket is its buttons. Blazers will have gold, silver or mother of pearl buttons.
Can be worn casually with jeans however brass or metal buttons can make it difficult

THE SPORTCOAT

Can be more casual than a blazer
Originally worn during “sporting” activities (hunting, shooting etc.)
The sports jacket was meant to look more rugged than the suit and the blazer. As such, sturdier fabrics were used such as tweeds, houndstooth and Donegal. Cotton and linens are also common fabrics used.
Often has less construction than a blazer or a suit jacket
Looks great dressed up or casually with jeans

SUIT JACKET

In most situations a suit jacket is intended to be worn with the matching trousers
Generally a suit jacket is made to fit slimmer. It should fit close to the body. It is also not meant to be worn with multiple layers underneath.
Often has more construction than a blazer or sportcoat (canvas lining, shoulder pads etc.)
Fabrics (often wool) are usually finer and smoother compared to sportcoats
The buttons on today’s suit jackets will usually be plastic. However higher end suits may come with horn or mother-of-pearl buttons.
Suit jackets will usually come with notched lapels. Occasionally peak lapels are used in suits.