Input is information, effort, or material you put into something to make it work or help it grow. When you enter numbers into a calculator, that's input. When you type on a computer keyboard, each keystroke is input. When a baker measures flour and sugar into a mixing bowl, those ingredients are inputs for making a cake.

The word often describes contributions that lead to a result. A scientist needs input from experiments to develop a theory. A teacher values input from students during class discussions because their ideas help everyone learn. When someone says “I'd like your input on this,” they're asking for your thoughts or suggestions.

In everyday conversation, people distinguish between input and output: input is what goes in, output is what comes out. A factory needs inputs like raw materials and workers' labor to create outputs like finished products. Your brain receives input from your five senses (sight, sound, smell, taste, touch) and produces output in the form of thoughts and actions. When you practice piano, you're providing input (time, effort, practice) that leads to output (better playing ability).