Needless means unnecessary or without any real purpose. When something is needless, it could easily be avoided or left out without causing any problems. A needless argument starts over something that doesn't really matter. Needless worry means fretting about something that probably won't happen or isn't worth the anxiety.

The word often appears in the phrase needless to say, which means “obviously” or “as you'd expect.” If you tell a friend that you stayed up past midnight reading an exciting book, you might add “needless to say, I was exhausted the next morning.” You're pointing out that the conclusion is so obvious it barely needs mentioning.

When something causes needless harm or difficulty, it means the problem could have been prevented. A needless mistake happens when someone wasn't paying attention to something they should have noticed. Needless complications make a situation harder than it has to be. The word carries a slight tone of frustration or regret, suggesting that whatever happened didn't have to happen at all.