The electrolytic capacitor is an important part of electronic equipment.

There is an old radio cassette in my room.

He is operating a radio-controlled helicopter.

My grandfather still uses an old transistor radio.

The car radio in my car has broken.

There is a new clock radio in my room.

In mathematics, the commutative law applies to addition and multiplication.

Let's exchange keys tomorrow.

Do you understand the necessity of this project?

That information is unnecessary.