Single Breasted Suit
Among men’s suit types, the single breasted suit is the most ubiquitous. The easiest way to spot one is to look for the inclusion of either one, two or three buttons along the seam, or just observe what about 99% of professional men wear to work to every day. By virtue of the single row of buttons, a single breasted suit usually exudes a narrower and tighter appearance. These suits are most frequently paired with notch lapels.
There are firm codes of conduct when it comes to buttoning a single breasted suit. For a one-button suit, you should button when standing and unbutton when sitting. For a two-button suit, you should button the top button when standing, unbutton it when sitting, and never fasten the lower button. When it’s a rare three-button suit, the top button is optional, the middle button is always fastened (whether you’re sitting or standing), and the lower button is never fastened.