Dictionary.com
definitions

infra-

a prefix meaning “below,” used, with second elements of any origin, in the formation of compound words: infrasonic; infrared.

RELATED CONTENT

Science Terms That We All Pretend To Know
In the spirit of scientific community and understanding, let's clear up some misconceptions around a few of the most misunderstood scientific terms. Let’s boldly go where no man has gone before.
READ MORE
A Long List of Affixes: Suffixes, Prefixes, and Combining Forms
Suffixes -able, -ible, -ile:  (form adjs) able to, fit to, worthy, capable; apt to; subject to being ~-ed -ac:  one affect with -ac, -al, -ane, -ar, -ary, -ch, -ese, -ic, -ical, -id, -ile, -ine, -ish, -ory:  like, of, pertaining to; characterized by -aceae:  families of plants -aceous, -ous:  resemblance to a substance; full of -acy, -age, -ance, -ancy, -asm, -dom, -ence, -ency, -hood, -ism, -ity, -ment, -mony, -ness, -ry, -ship, …
READ MORE

Origin of infra-

< Latin, representing infrā, adv. or preposition
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for infra-

infra-

prefix

below; beneath; afterinfrasonic; infralapsarian

Word Origin for infra-

from Latin infrā
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
Word Origin and History for infra-

word-forming element from Latin infra (adv., prep.) "below, underneath, beneath; later than, smaller, inferior to," from PIE *ndher "under" (cf. Sanskrit adnah "below," Old English under "under, among;" see under). Opposed to super-. Its use as a prefix was rare in Latin.

Online Etymology Dictionary, © 2010 Douglas Harper
Medicine definitions for infra-

infra-

pref.

Inferior to, below, or beneath:infrasonic.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.