Arctic Circle |
an imaginary line drawn around the earth parallel to the equator which marks the boundary of the Arctic. North of this line there are periods of continuous night in the winter and continuous day in the summer. |

barrier island |
a long narrow island that is parallel to the mainland. A barrier island helps protect the shore from being worn away by the action of the ocean's waves. |

cylinder |
a solid figure with a shape similar to that of a can, a round flat cake, or a round tube with closed ends. A cylinder has parallel circular faces joined by one curved face. |

even |
at the same level or height; parallel. [1/12 definitions] |

grate^{1} |
a frame of crossed or parallel metal bars used as a covering or guard over an opening. [1/2 definitions] |

grid |
a frame of crossing or parallel bars; grating. [2 definitions] |

horizontal |
parallel to the surface of the earth or to the horizon. |

level |
being on a line with the horizon or parallel to the ground. [2/10 definitions] |

parallel |
lying or moving in the same direction and being the same distance apart at every point. Parallel lines never meet or cross each other. [1/5 definitions] |

parallelogram |
a flat closed figure with four straight sides. The opposite sides are parallel and equal to each other. |

prism |
a solid figure that has parallel bases that are the same size and shape and faces that are parallelograms. [1/2 definitions] |

rectangle |
a flat, closed figure with four straight sides, four right angles, and opposite sides parallel to each other. |

rhombus |
a flat, closed figure in which all four sides are equal in length, and both pairs of opposite sides are parallel. |

staff^{1} |
the set of five parallel lines and the empty spaces between them on which music notes are written. [1/5 definitions] |

trapezoid |
a flat, closed figure with four straight sides. Of these sides, only two are parallel. [1/2 definitions] |

uneven |
not straight, level, or parallel. [1/5 definitions] |