Single breasted is a term used to refer to a style of suit coat or jacket where there is only one row of buttons used to close the front of the jacket or coat. This is in contrast to a double-breasted jacket which has two rows of buttons used to close the front of the garment.
Typically a single breasted jacket has anywhere from 2 to 3 buttons however this is not a requirement of the style. Most often changing the lapel style on single breasted jacket is a way of adding variety to this classic style. Unlike other types of jackets that have strict rules on what is and is not appropriate for a lapel; a single breasted jacket can have any lapel style that the designer or client wishes while still maintaining a single breasted sensibility.