Useless means having no practical value or being unable to accomplish anything worthwhile. A broken pencil sharpener that mangles your pencils instead of sharpening them is useless. A flashlight with dead batteries is useless when you need light in the dark.

Something becomes useless when it can't do what it's supposed to do. A map is useless if it shows the wrong roads. Instructions are useless if they're written in a language you don't understand. An umbrella is useless in a windstorm if it flips inside out.

People sometimes say they feel useless when they can't help with a problem or contribute to a group effort. Maybe you watch your older siblings build something complicated while you're too young to help, or you sit on the sidelines with an injury while your team plays. That frustrated feeling of wanting to be useful but not knowing how is part of being human, and it usually passes as you learn new skills or find different ways to contribute.

The opposite of useless is useful: a sharp pencil, a working flashlight, or a skill you can apply when it matters.