The word click has several meanings:

1. A short, sharp sound like when you press a pen, snap your fingers, or turn a light switch. The sound happens quickly and crisply: click. A camera makes a clicking sound when you take a picture. Tap dancers' shoes click against the floor. When you hear your seatbelt click into place, you know it's fastened securely.
2. To press a button on a computer mouse or touchpad. When you click on an icon, you're selecting it. You might click a link to open a website, or double-click to open a file.
3. When things suddenly make sense or work well together. You might struggle with a math concept for days, then suddenly it clicks and you understand. When two people become instant friends, you might say they clicked right away. The moment something clicks, it's like a lock opening or puzzle pieces falling into place. Your brain makes a connection it couldn't make before.
4. A unit for measuring distance on old-fashioned military maps, equal to one kilometer. Soldiers might say a target is “five clicks away,” meaning five kilometers.