Aaron Marino of alpha m. discusses the differences between an overcoat and topcoat.
Overcoat
The overcoat is full length. It’s designed to be over a suit or sport coat, is typically double breasted, and is typically wool or cashmere.
Topcoat
The topcoat is made of wool or cashmere but is generally lighter weight. It’s single breasted and three quarter length. It hits at the knee or just below. The topcoat can be worn more casually, such as with jeans. The topcoat is the more optimal choice of the two because it’s more refined with cleaner lines. You can dress it up or dress it down.
