infra-youdaoicibaDictYouDict[infra- 词源字典]
word-forming element from Latin infra (adv., prep.) "below, underneath, beneath; later than, smaller, inferior to," from PIE *ndher "under" (cognates: Sanskrit adnah "below," Old English under "under, among;" see under). Opposed to super-. Its use as a prefix was rare in Latin.[infra- etymology, infra- origin, 英语词源]