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Also available:
World English Dictionary
Dictionnaire Français
principal point
prin·ci·pal point
(
plural
prin·ci·pal points
)
noun
Definition:
point where principal planes cross axis:
either of two points in an optical system where the two principal planes cross the optical axis
Encarta® World English Dictionary [North American Edition] © & (P)2009 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.
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