I have 4 sides.

I have 4 corners/vertices.

I have 4 right angles.

My sides are all the same length.

You might see me as a window or a cushion.

I have 3 sides.

I have 3 corners/vertices.

I could have right, acute and obtuse angles.

You might see me as a coat hanger or a pizza slice.

I have 1 side.

I have 0 corners/vertices.

My side is not straight.

You might see me as a button or clock.

I have 5 sides.

I have 5 corners/vertices.

If I am a regular shape, I have 5 obtuse angles.

You might see me as a house or teabag.

I have 4 sides and they are usually 2 different lengths.

I have 4 corners/vertices.

I have 4 right angles.

You might see me as a book or a piece of paper.