The arm is the part of your body between your shoulder and your hand. You use your arms to throw a ball, carry groceries, give hugs, and do countless other tasks every day. Your arm contains bones, muscles, and joints that work together to lift, push, pull, and swing.

The word also means weapons or the act of preparing for conflict. Countries build up their arms (weapons and military equipment) to defend themselves. When a nation arms itself, it acquires weapons and trains soldiers. You might read about an arms race between countries competing to have stronger militaries, or arms control agreements that limit weapons. The phrase “take up arms” means to prepare for battle.

In another sense, arm can mean to equip someone with what they need. A teacher might arm students with knowledge before a difficult test. You could arm yourself with facts before a debate. This usage suggests giving someone tools or information that help them succeed or protect themselves.

You'll also see arm refer to something that extends from a main body, like the arm of a chair (where you rest your arms while sitting) or an arm of a starfish reaching out from its center.