something with a round shape resembling a flat circular plate | disc; disk; saucer; |

a toroidal shape | anchor ring; annulus; doughnut; halo; ring; |

anything with a round or oval shape (formed by a curve that is closed and does not intersect itself) | loop; |

a loop in a rope | bight; |

a round shape formed by a series of concentric circles (as formed by leaves or flower petals) | coil; curl; curlicue; gyre; ringlet; roll; scroll; whorl; |

a plane curve traced by a point circling about the center but at increasing distances from the center | spiral; |

a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle | helix; spiral; |

a pair of parallel helices intertwined about a common axis | double helix; |

a curve that reverses the direction of something | perversion; |

(geometry) a ratio describing the shape of a conic section; the ratio of the distance between the foci to the length of the major axis | eccentricity; |

a straight line that generates a cylinder or cone | element; |

a straight line joining the apex and a point on the base | element of a cone; |

a straight line running the length of the cylinder | element of a cylinder; |

the constant angle at which a helix cuts the elements of a cylinder or cone | helix angle; |

a sharp bend in a line produced when a line having a loop is pulled tight | kink; twirl; twist; |

the shape of something rotating rapidly | convolution; swirl; vortex; whirl; |

a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it | ellipse; oval; |

(geometry) a plane rectangle with four equal sides and four right angles; a four-sided regular polygon | foursquare; square; |

something approximating the shape of a square | square; |

a square-shaped object | quadrate; |