Prefix · position · below
Means "below" or "beneath a threshold": infrastructure, infrared, infrasound, infrasonic.
Written by Bryan López, English teacher · Updated
Infra- comes from Latin "infra" (below, beneath, under) and signals something is beneath a level, boundary, or threshold. Infrastructure = the structure beneath (the base that supports everything); infrared = below red (frequencies below visible red light); infrasound = sound below the threshold of human hearing. Spanish uses the same prefix: infraestructura, infrarrojo, infrasonido.
In physics: infrared (heat radiation below visible light), infrasonic (sound below 20 Hz). In engineering: infrastructure, infrastructural. In medicine: infrarenal (below the kidney). Because Spanish uses the identical prefix "infra-", every English infra- word has a transparent Spanish cognate.
Combines with nouns and adjectives to mean "below" in level, position, or scale:
Pronunciation: /ˈɪn.frə/. Spanish uses the identical prefix "infra-". Cognates: infraestructura (infrastructure), infrarrojo (infrared), infrasonido (infrasound), infrahumano (infrahuman). Do not confuse with in- (negation) or inter- (between).
infra-/ˈɪn.frə/
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Separate prefixes with separate origins: in- (negation) from Latin "in-" (not/without); infra- from Latin "infra" (down/below). Tip: if the word means the opposite of something, it is in-; if it means something is beneath a level, it is infra-.
A trick to remember it
Infra- = below, beneath. Direct Spanish cognates: infraestructura (infrastructure), infrarrojo (infrared), infrasonido (infrasound). Spanish uses the identical prefix, so every infra- word you know in Spanish maps directly to English.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What do infrared cameras detect?
The prefix infra- means "below" or "beneath a threshold": infrastructure, infrared, infrasound, infrasonic. In Spanish it usually maps to infra-.
The prefix infra- is pronounced /ˈɪn.frə/. For example, "infrastructure".
"structure" becomes "infrastructure". It is a typical example of the infra- prefix.
un-, re-, pre-, dis-, over-, in-... every beginning you need to unlock thousands of English words at once.