9 examples of key
a watch key; a bed key; the winding key for a clock, etc.
the keys of a piano, an organ, an accordion, a computer keyboard, or of a typewriter.
the key of a line of defense; the key of a country; the key of a political situation
the key to a riddle; the key to a problem.
a telegraph key
he dominates play in the paint
an example that was fundamental to the argument
computers are fundamental to modern industrial structure
the central cause of the problem