What are the shapes in Japanese?
I havn't been able to find a translation from English to Japanese of the geometrical shapes such as square, circle, triangle, rectangle, ect. can anyone help?

Question

Answer

I don't know them all but here are some

Circle = En/Maru
Triangle = Sankakkei / Sankaku
Square = Seihoukei / Mashikaku 
Rectangle = Chouhoukei/ Nagashikaku 
Oval/ Ellipse = Daen 
Trapezoid = Daikei

Answer

I can add a couple more:

Hexagon = rokkakukei （六角形）
Octagon = hakkakkukei（八角形）

(so the number of angles corresponds to kakukei (or kakkei in a slang).