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[pin-yool] /ˈpɪn yul/
  1. a part or organ resembling a barb of a feather, a fin, or the like.
  2. a finlet.
Botany. a secondary pinna, one of the pinnately disposed divisions of a bipinnate leaf.
a metal plate with a small hole in it, used as a sight in a quadrant.
Origin of pinnule
1585-95; < Latin pinnula pinnula
Related forms
[pin-yuh-ler] /ˈpɪn yə lər/ (Show IPA),
adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for pinnule
Historical Examples
  • The index reference for "pinnule" should probably be 59, rather than 66, but was not changed.

  • pinnule, a secondary division of a bipinnate or tripinnate leaf, 66.

  • Sporangia in oblong sori under a reflexed tooth of a pinnule; indusium broad; rachis dark and shining.

    The Fern Lover's Companion George Henry Tilton
  • The sori are placed on small veins which grow outwards from the midrib of the pinnule.

    How to Know the Ferns S. Leonard Bastin
  • They occur about midway between the central vein of the pinnule and the margin of the leaf.

    How to Know the Ferns S. Leonard Bastin
  • The sori are in the form of lines which branch out from the lower part of the pinnule in a fan-shaped manner.

    How to Know the Ferns S. Leonard Bastin
British Dictionary definitions for pinnule


noun (pl) pinnules, pinnulae (ˈpɪnjʊˌliː)
any of the lobes of a leaflet of a pinnate compound leaf, which is itself pinnately divided
(zoology) any feather-like part, such as any of the arms of a sea lily
Derived Forms
pinnular, adjective
Word Origin
C16: from Latin pinnula, diminutive of pinna feather
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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pinnule in Science
Any of the smaller leaflets into which each leaflet of a bipinnately compound leaf is subdivided. The leaves of many ferns are divided into pinnules.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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