There are many people who cannot differentiate between A tuxedo and suit. The difference are as follows.

1. In a tuxedo the Lapel is made of satin fabric. Satin is a smooth, glossy fabric, normally made of silk, produced by a weave in which the threads of the warp are caught and looped by the weft only at certain intervals.
In a suit the lapel and the fabric of the suit are same.

2. In a tuxedo the buttons are covered where as you find regular buttons in case of suit.

3. Trousers of the tuxedo will have satin piping’s on the seam whereas the trousers worn with the suit will have no piping’s.