A.shin <*>, Phoenician Ω , Syria 6.103), but eighteenth of the Ion. alphabet: as numeral ς´ = 200, but σ᾽ = 200,000: a semi-vowel, Arist.Po.1456b28, cf. Pl.Tht.203b.
A. the oldest forms expressing this sound were Μ (which is however the old eighteenth letter, q.v.), also Σ and ς ; compared to a twisted curl, E.Fr.382.7, Theodect.6; to a Scythian bow, Agatho 4; after this, but yet early, it took the shape of a semicircle <*>, whence Aeschrio (Fr.1) calls the new moon τὸ καλὸν οὐρανοῦ νέον σῖγμα: hence the orchestra is called τὸ τοῦ θεάτρου σῖγμα, Phot., AB 286: and Lat. writers used sigma of a semicircular couch, Mart.10.48.6, etc.; cf. σιγμοειδής. The rare form <*> is used in the numbering of building-stones in Berl.Sitzb.1888.1234, 1242 (Pergam.). From final ς must be disting uished the character ς = 6, v. ϝ ϝ (sixth letter).
B. the name σίγμα ( σῖγμα ) was usu. indeclinable, “τοῦ σῖγμα” Pl. l.c., Cra.402e, 427a, Ath.10.455c, Lyd.Mens.1.21 (v.l. σίγματος）“; τῷ σῖγμα” Gal.UP2.14, al.; “τῶν σῖγμα” Pl.Com.30; “τὰ σίγμα τὰ ἐπὶ τῶν ἀσπίδων” X.HG4.4.10, cf. Hellad. ap. Phot.Bibl.p.532 B.; later declined, “τοῦ σίγματος” Eust.1389.15; “σίγμασιν” Id.905.7.
2. we also hear of another name σάν [α^], τό, τὰ οὐνόματά σφι (sc. τοῖσι Πέρσῃσι）“ τελευτῶσι πάντα ἐς τὠυτὸ γράμμα, τὸ Δωριέες μὲν σὰν καλέουσι, Ἴωνες δὲ σίγμα” Hdt.1.139, cf. Pi.Dith.Oxy.1604 Fr. 1 ii 3, Ath.11.467a; as name of the fourth and tenth letters in Θρασύμαχος, and of the sixth in Διονύσο（υ), Epigr. ap. Ath.10.454f, Achae.33.4; cf. the compd. σαμ-φόρας: σάν and σίγμα were evidently pronounced alike; it is conjectured that σάν is originally the name of the old eighteenth letter.