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Waste (or wastes) are unwanted or unusable materials. Waste is any substance that is discarded after primary use or is worthless, defective, and of no use.
It may be no longer useful as it has served its purpose, and at the end of the process have no further use, and is generally discarded. It is unwanted material that people have thrown away. It is often also called trash, garbage, rubbish, or junk. It can be solid, liquid, or gas, or it can be waste heat. There are many different kinds of waste. Garbage is the waste we produce daily in our homes, including old or unwanted food, chemical substances, paper, broken furniture, used containers, and other things.
When waste is a liquid or gas, it can be called an emission. This is usually pollution. Sanitation is the proper handling of human waste.
Waste can also be something abstract (something that you cannot touch), for example, "a waste of time" or "wasted opportunities". When people use the words waste or wasted in this way, they are saying (directly or indirectly) that something has been used badly (using too much of it or using it incorrectly).
People have thrown away waste in heaps for thousands of years. In modern homes and businesses, garbage is normally placed in waste containers of some sort. It is then moved to the streets, where it can be collected and taken to a place designed to hold, destroy, or recycle garbage. Some waste materials, such as paper, wood, glass, metals, and plastic containers, can be recycled (reused). Materials that cannot be recycled are either burned (incinerated) or heaped into landfills.
Plant matter, such as fruit and vegetable scraps, is biodegradable. It can usually be heaped into a compost, where it will decompose relatively quickly. This kind of waste is often called "wet" or "green" waste.
Very often, waste is not collected in containers. It may instead be thrown onto the ground or dumped somewhere. This is called littering.
Media related to Waste at Wikimedia Commons
A description about the different sources of waste including classification of waste.