Lewis Short
penna | pinna | pesna | petna (noun F) : or (old forms, , , Fest. p. 205, 209 Müll.), orig. different words, penna for petna; root petor pat-; Sanscr. patāmi, to fly; Gr. πέτομαι, prop. a wing: pinna for pitna; cf. Sanscr. pitu; Gr. πίτυς, the pine-tree; Lat. pinus; cf.: spiculum, spina; prop. a sharp point or end. To a late period an effort was made to distinguish them: nec miretur (puer), cur ... fiat a pinno quod est acutum, securis utrimque habens aciem bipennis, ne illorum sequatur errorem, qui, quia a pennis duabus hoc esse nomen existimant, pennas avium dici volunt,Quint. 1, 4, 12 Halm: pinnum enim antiqui acutum dicebant,Isid. Orig. 19, 19, 11 dub. (v. 1. pennus): pinnas murorum, pennas avium dicimus, Flav. Cap. p. 2243 P. This dictum of the old grammar we have to retain, although the distinction is neither etymologically sound nor is it always practically true; cf. bipennis, Bramb. Lat. Orthog. p. 118. In MSS. and edd. the two forms have mostly been used indiscriminately in all meanings except II. D. E. F. infra, in which pinna only is found; cf. esp. Wagn. Orth. Verg. p. 465; Rib. prol. Verg. p. 441 sq.; Corss. Ausspr. 2, p. 270 sq.
* A feather on the body of a winged creature (syn. pluma).
* Lit.
* Form penna: sine pennis volare haud facile est: meae alae pennas non habent,Plaut. Poen. 4, 2, 48: pennarum tuarum nitor,Phaedr. 1, 13, 6: maduere graves aspergine pennae,Ov. M. 4, 728.
* Transf.
* In plur.: pennae (pinnae), a wing (syn. ala).
* In mechanics.
* A feather on an arrow (poet.).
* Poet., a flying, flight.
* In late Lat., a pen.—Form penna: instrumenta scribae, calamus et penna: sed calamus arboris est, penna avis,Isid. Orig. 6, 14.
* A fin. —Form pinna, Plin. 9, 13, 15, § 42.
* A pinnacle.—Form pinna: turres contabulantur, pinnae loricaeque ex cratibus attexuntur,Caes. B. G. 5, 39; 7, 72: milites Metelli ... a pinnis hostis defendebant facillime funditore, Quadrig. ap. Gell. 9, 1, 1; Verg. A. 7, 159: templi,Vulg. Luc. 4, 9.
* Meton., an arrow (poet.).
* Form penna: cervos pennā petere,Val. Fl. 6, 421.
* Form pinna: olor trajectus pinnā,Ov. F. 2, 110.
* A float or bucket of a water-wheel.—Form pinna, Vitr. 10, 10.
* A stop or key of a water-organ.— Form pinna,Vitr. 10, 13.
Charlton T. Lewis, Charles Short, A Latin Dictionary