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per·pen·dic·u·lar (pûrpən-dĭkyə-lər)
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adj.
1. Mathematics Intersecting at or forming right angles.
2. Being at right angles to the horizontal; vertical. See Synonyms at vertical.
3. often Perpendicular Of or relating to a style of English Gothic architecture of the 1300s and 1400s, characterized by the use of fan vaulting and broad windows with many mullions.
adv.
In a perpendicular position.
n.
1. Mathematics A line or plane perpendicular to a given line or plane.
2. A perpendicular position.
3. A device, such as a plumb line, that is used in marking the vertical from a given point.
4. A vertical or nearly vertical line or plane.

[Middle English perpendiculer, from Old French, from Latin perpendiculāris, from perpendiculum, plumb line, from perpendere, to weigh carefully : per-, per- + pendere, to weigh; see (s)pen- in the Appendix of Indo-European roots.]

perpen·dicu·lari·ty (-lărĭ-tē) n.
perpen·dicu·lar·ly adv.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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