Waste means to use something carelessly or let it be destroyed without getting value from it. When you throw away half your lunch because you weren't hungry, you waste food. When you spend an hour watching videos instead of finishing your homework, you waste time. When you leave lights on in empty rooms all day, you waste electricity.

The word carries a sense of loss: something valuable disappears without accomplishing anything useful. A talented musician wastes her abilities if she never practices. A team wastes an opportunity when they don't take advantage of their opponent's mistake. Money gets wasted when spent on something that breaks immediately or never gets used.

Waste can also be a noun meaning garbage or unwanted material. Factories produce industrial waste. Your body produces waste that gets flushed away. Cities must figure out where to put all their waste.

The word wasteful describes someone who wastes things habitually, like a wasteful spender who buys things they don't need and can't afford. Being wasteful matters because resources are limited: wasted time can never be recovered, wasted money can't be spent again, and wasted opportunities may not come back.