To tell means to give information to someone using words. When you tell your friend about your weekend, you're sharing what happened. When a teacher tells the class to line up, she's giving instructions. You might tell a joke, tell the truth, or tell someone your name.

The word appears in many common expressions. You can tell time by reading a clock, or tell the difference between two similar things (like identical twins). If someone asks “Can you tell?” they're wondering if you can notice or recognize something. When you tell someone off, you scold them firmly. A telltale sign reveals something that was supposed to be hidden, like muddy footprints that are telltale evidence of who tracked dirt through the house.

Sometimes tell means to have a noticeable effect: if you stay up too late, lack of sleep will tell on you the next day when you're exhausted. In card games, a tell is an unconscious behavior that reveals what cards someone holds.

The past tense is told. When you've already shared information, you've told someone. And if you're counting things, you might say “All told, there were twenty people at the party,” meaning when you count everything up.