To remember a Radian - Think radius and angle

It’s easy to remember what a radian is because it’s a combination of its name:

Also

The name radian in sound emphasises that it is a raid (of a radius).

A radian is a radius on a circumference to give an angle.

A raid (radian) by a radius on a circumference.

When you talk about the radius of a circle you should recognise that it is closely coupled to a circumference.