half
One of two equal parts of a whole thing.
Half means one of two equal parts that make up a whole. If you split a sandwich down the middle and give one piece to your friend, you've each got half. If your teacher asks you to read half the chapter, you stop at the midpoint.
Half can be written as the fraction ½ or as 0.5 in decimal form. When you cut a pizza into two equal slices, each slice is half the pizza. When you're halfway through a movie, you've watched half of it and have half remaining.
The word works in lots of everyday situations. If you and your sister split the cost of a gift, you might each pay half. If someone says they're half asleep, they mean they're somewhere between fully awake and completely asleep. When a glass is half full, it contains 50% of what it could hold.
You'll also hear half used for emphasis or exaggeration: “I'm half starving” doesn't mean literally half dead from hunger, just very hungry. “Half the class” might mean a large portion even if it's not exactly 50%. And when someone does something half-heartedly, they're putting in partial effort rather than their full commitment.
The plural is halves, which sounds like “havz”: two halves make a whole.