ptero-

Also petə-, Proto-Indo-European root meaning "to rush, to fly." 

It forms all or part of: accipiter; appetence; appetite; apterous; apteryx; archaeopteryx; asymptote; centripetal; Coleoptera; compete; competent; eurypterid; feather; helicopter; hippopotamus; Hymenoptera; impetigo; impetuous; impetus; iopterous; Lepidoptera; ornithopter; panache; panne; pen (n.1) "writing implement;" pennon; peripeteia; perpetual; perpetuity; petition; petulance; petulant; pin; pinion; pinnacle; pinnate; pinniped; potamo-; potamology; propitiation; propitious; ptero-; pterodactyl; ptomaine; ptosis; repeat; symptom.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pattram "wing, feather, leaf," patara- "flying, fleeting;" Hittite pittar "wing;" Greek piptein "to fall," potamos "river, rushing water," pteron, pteryx "feather, wing," ptilon "soft feathers, down, plume;" Latin petere "to attack, assail; seek, strive after; ask for, beg; demand, require," penna "feather, wing;" Old Norse fjöðr, Old English feðer "feather;" Old Church Slavonic pero "feather;" Old Welsh eterin "bird."

raptorial bird, 1708, from Latin accipiter, a generic name for birds of prey, especially the common hawk. According to de Vaan, "generally assumed" to be from a Proto-Italic *aku-petri- "having pointed (that is, 'swift') wings" (see acro- + ptero-) and compares Greek okypteros "with swift wings," Sanskrit asu-patvan- "flying swiftly," "all of which are used as epithets to birds of prey." Under this theory the initial acc- is by influence of the verb accipere "to take" (whence also Latin acceptor "falcon;" see accept). Or the sense could be literal, "with pointed wings." The proper plural would be accipitres. Related: Accipitral; accipitrine (1809).