noun

der Knopf, ¨-e

button

Ein kleines rundes Teil, das man drückt oder an Kleidung befestigt, um etwas zu schließen oder zu bedienen.

The German word "Knopf" is a noun that means "button" (e.g., on clothing or a device). It denotes a small, typically round object sewn onto garments for fastening or used on devices to activate a function.

Similar words:

Schalter (switch)
Knöpfchen (diminutive form, small button)
Taste (key/button, e.g. on a keyboard or piano)

Differences:

Knopf usually refers to clothing buttons or simple mechanical buttons.
Schalter implies a switch, often electrical or more complex.
Taste is often used for flat keys/buttons on electronic instruments or devices.
Knöpfchen is just a smaller or more affectionate term for "Knopf."