Waste (or wastes) are unwanted or unusable materials. Waste is any substance which 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 it is generally discarded. It is unwanted materials and objects 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.
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 street, 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.