I covered a bit about how lapels are constructed in my last two Suit Construction articles, so I thought I might expand a bit on it here, but focus more on the design aspects.
There are three types of lapels; Notched, Peaked, and Shawl.
The Notch Lapel
A notched lapel is perhaps the most common, simply because it is cheaper and easier to produce than the peaked lapel. The notch lapel gets its name from the triangular gap between where the collar meets the top of the lapel. It is also known as a step lapel.
Where It’s Used: The most common of the three lapels, the notch lapel is found everywhere from blazers and sportcoats, to business suits. It should never be worn on a dinner jacket (unless you are a waiter, then just wear what they tell you).
The Peak Lapel
The Peak lapel is the most formal, and is featured prominently on Double-Breasted Jacket, as well as Dinner Jackets. Traditionally speaking, this was the only lapel that would be on either of these jackets, but standards have fallen over time. The peak lapel gets its name from the peak formed when the top of the lapel meets the bottom of the collar.
Where It’s Used: Primarily on Double-Breasted and Dinner jackets, but it is also found on everyday business suits, and the occasional casual jacket.
The Shawl Lapel
Originating on the Smoking Jacket, the shawl lapel is now found primarily on the Dinner Jacket. A slightly more casual alternative to the peak lapel, the shawl lapel is characterised by it’s single, rounded edge; with no break to distinguish the lapel from the collar.
Where It’s Used: On Dinner Jackets and Smoking Jackets only.
Check out this article by Black Lapel for more details.