A modicum is a small amount of something, usually just barely enough to matter or make a difference. If your teacher says you need to show a modicum of effort to pass the class, she means you need at least some real try, not zero effort. If someone asks for a modicum of respect, they're asking for just a basic, minimum level of courtesy.

The word often appears when someone is pointing out that even a little bit would help or would be appreciated. A coach might tell a losing team that with a modicum of focus, they could turn things around. A parent might say that keeping your room clean requires only a modicum of discipline: not perfect organization, just a little self-control.

Modicum emphasizes that something is in short supply or barely present. You wouldn't say someone has a modicum of talent if they're actually quite skilled. You use it when there's just a small trace of something, often when more would be better, but you'll settle for a little.