actino-

actino-

or actin-

pref.

1. Radial in form: actinoid.

2. Actinic radiation: actinometer.

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[From Greek aktīs, aktīn-, ray; see nek^w-t- in Indo-European roots.]

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

actino-

or before a vowel

actin-

combining form

1. indicating a radial structure: actinomorphic.

2. indicating radioactivity or radiation: actinometer.

[from Greek aktino-, from aktis beam, ray]

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

actino-

a combining form with the meaning “ray, beam,” used with the particular senses “radiation” in the physical sciences (actinometer) and “having raylike structures,” “radiate in form” in biology (actinomyces).

[< Greek, comb. form representing aktis, genitive aktînos ray, beam; see -o-]

Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.