有关收敛的平面图形，除三角形外?

semicircle                         半圆?

concentric circles                 同心圆?

quadrilateral                      四边形?

pentagon                           五边形?

hexagon                            六边形?

heptagon                           七边形?

octagon                            八边形?

nonagon                            九边形?

decagon                            十边形?

polygon                            多边形?

parallelogram                      平行四边形?

equilateral                        等边形?

plane                              平面?

square                             正方形，平方?

rectangle                          长方形?

regular polygon                    正多边形?

rhombus                            菱形?

trapezoid                          梯形