Sartorial Suggestions: For the Record…

[octothorpe]

It seems so elementary, but I keep seeing these terms used incorrectly, so I am clarifying them.

Button-Up

A shirt that buttons in the front. Contrast this with a "pullover"

Button-Down (aka Buttoned-Down)

A shirt whose collar can be stayed through the use of buttons

Not all button-down shirts are button-up, and vice versa.

A button-down shirt is actually a more casual shirt than a button-up shirt. The buttons were used so the collar wouldn't flap in the wind while outside playing sports (polo, etc). Do not wear a button-down shirt to a formal occasion, unless you are specifically dressing down and belittling your hosts.