Cross Section
Pronunciation: /ˈkrɔs ˈsɛk.ʃən/ Explain

Figure 1: Stack of coins. 
 In geometry, a cross section is a section made by cutting an object with
a plane. Cross sections are important in the study of math.
Cavalieri's principle
states that, if the volumes of the cross sections of two
3dimensional
geometric
figures
are equal, then the volumes of the two figures is the same. This is illustrated by a stack
of coins. It doesn't matter how the coins are stacked, the volume of the stack of coins
remains the same. Cavalieri's principle leads the way to infinitesimal calculus.
 In statistics, a cross section is a sample of data believed to be
representative.
Examples of Geometric Cross Sections

Figure 1: Cross section of a tree trunk. 

Figure 2: Cross section of a car engine. 

Figure 3: Cross section of the earth's crust. 
References
 McAdams, David E.. All Math Words Dictionary, cross section. 2nd Classroom edition 201501084799968. pg 51. Life is a Story Problem LLC. January 8, 2015. Buy the book
Cite this article as:
McAdams, David E. Cross Section. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/c/crosssection.html.
Image Credits
 All images and manipulatives are by David McAdams unless otherwise stated. All images by David McAdams are Copyright © Life is a Story Problem LLC and are licensed under a Creative Commons AttributionShareAlike 4.0 International License.
 Stacks of coins: Anton, http://commons.wikimedia.org. Licensed under the terms of the GNU Free Documentation License, Version 1.2 or any later version.
 Cross section of a tree trunk: Arnoldius Benutzer, https://commons.wikimedia.org. This file is licensed under the Creative Commons AttributionShare Alike 2.5 Generic license. https://commons.wikimedia.org/wiki/File:Tree_rings.jpg.
 Cross section of a car engine: Beau Daniels and Alan Daniels. © Beaudaniels.com. All rights reserved. Reproduced by permission .
 Cross section of the earth's crust: Jeremy Kemp, Ed.D., M.Ed., M.S.J., https://commons.wikimedia.org. This work has been released into the public domain by its author, Jeremykemp at English Wikipedia. https://commons.wikimedia.org/wiki/File:Earthcrustcutawayenglish.png.
Revision History
12/21/2018: Reviewed and corrected IPA pronunication. (
McAdams, David E.)
6/25/2018: Removed broken links, updated license, implemented new markup, updated GeoGebra apps. (
McAdams, David E.)
5/5/2011: Initial version. (
McAdams, David E.)