We’ve assembled the handy guide below, ordered from the humblest options to the fanciest, to help you navigate this terrain.

So what is semi-formal for men ... In summer, light gray or khaki linen and cotton suits are acceptable but make sure they’re refined—not as though you’ve wandered in from a beach resort.

A double-breasted jacket features two overlapping buttons which cross at the front. “Double-breasted [suits are] made in ...