word-forming element meaning "air, atmosphere; gases," in 20c. use with reference to aircraft or aviation, from Greek aēr (genitive aeros) "air, lower atmosphere" (see air (n.1)).

"pertaining to ships, sailors, or navigation," 1550s, from -al (1) + nautic from French nautique, from Latin nauticus "pertaining to ships or sailors," from Greek nautikos "seafaring, naval," from nautēs "sailor," from naus "ship" (from PIE root *nau- "boat").

in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.

"underwater explorer," 1881, in a futuristic novel, from aqua- "water" + ending perhaps from aeronaut (attested by 1784; see aeronautics), ultimately from Greek nautēs "sailor" (from PIE root *nau- "boat").

nāu-, Proto-Indo-European root meaning "boat."

It forms all or part of: aeronautics; aquanaut; Argonaut; astronaut; cosmonaut; nacelle; naval; nave (n.1) "main part of a church;" navicular; navigate; navigation; navy; naufragous; nausea; nautical; nautilus; noise.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit nauh, accusative navam "ship, boat;" Armenian nav "ship;" Greek naus "ship," nautes "sailor;" Latin navis "ship;" Old Irish nau "ship," Welsh noe "a flat vessel;" Old Norse nor "ship."