ἰός

English (LSJ)

(A) [ῑ], ὁ, pl. ἰοί, heterocl.

   A ἰά Il.20.68 (Cypr., acc. to AB1095):— arrow, ἰὸν ἕηκε Il.1.48; βλήμενος ἢ ἰῷ ἢ ἔγχεϊ 8.514, cf. A.Pers.461; ἧκεν κομήτην ἰόν S.Tr.567. (Cf. Skt. í[snull ] 'arrow'.)
ἰός (B) [ῑ], ὁ,

   A poison, as of serpents, A.Eu.478, S.Tr.771, E.Ion 1015, Plu.2.562c, etc.; venom of a mad dog, Ruf.Fr.118; ἰὸς ἀμεμφὴς μελισσῶν, of honey with which snakes fed Iamos, Pi.O.6.47: metaph., of envy, A.Ag.834. (Cf. Skt. vi[snull ]ám 'poison', Lat. vīrus.)
ἰός (C) [ῑ], ὁ,

   A rust on iron, or verdigris on copper and bronze, Sapph.141 (dub.), Thgn.451, Pl.R.609a, Ti.59c, Theoc.16.17; ἰ. σιδήρου Dsc.5.80; ἰ. χαλκοῦ Hp.Mul.1.75, Dsc.5.79, Gal.12.218; patina on bronze statues, ὅπως καθαρὸς ἰοῦ ἔσται ὁ ἀνδριάς SIG284.15 (Chios, iv B.C.), cf. Plu.2.395b. (Perh. identical with ἰός B.)
ἰός [ῐ], ἴᾰ, ἰόν,

   A one, commonest in fem. (v. εἷς): neut. ἰῷ κίον ἤματι Il.6.422: masc. dat. ἰῷ, = ἐκείνῳ, Leg.Gort.8.8; but, = ἑνί, ib.7.23; acc., τόν γ' ἰὸν ἐνιαυτόν the same year, IG5(1).1390.126 (Andania, i B.C.); ἰός, = μόνος, acc. to Trypho ap.A.D.Pron.56.4.

Greek (Liddell-Scott)

ἰός: ῑ, ὁ, πληθ. ἰοί, ἀλλ’ ὡσαύτως ἑτερογεν. ἰά, Ἰλ. Υ. 68: ― βέλος, ἰὸν ἔηκε Ἰλ. Α. 48˙ βλήμενος ἢ ἰῷ ἢ ἔγχεϊ Θ. 514˙ οὕτω παρὰ Τραγ., Αἰσχύλ. Πέρσ. 461˙ ἧκεν κομήτην ἰόν, ἔρριψε πτερωτὸν βέλος, Σοφ. Τρ. 567. ΙΙ. σκωρία, ἰδίως ἡ τοῦ σιδήρου ἢ τοῦ χαλκοῦ, Λατ. ferrugo, aerugo, Θέογν. 451, Πλάτ. Πολ. 609Α, Τίμ. 59C, Θεόκρ. 16. 17. 2) δηλητήριον, οἷον τὸ τῶν ὄφεων, Αἰσχύλ. Ἀγ. 834, Εὐμ. 478, Σοφ. Τρ. 771, Εὐρ. Ἴων 1015, Πλούτ. 2. 562C, κλ.˙ ὁ Πίνδ. περὶ μέλιτος λέγει, ἰὸς ἀμεμφὴς μελισσῶν, ἀλλ’ ἀναφορικῶς πρὸς τοὺς δράκοντας τοὺς θρέψαντας τὸν Ἴαμον, Ο. 6. 79. (Αἱ δύο λέξεις παράγονται ἐκ διαφόρων ῥιζῶν˙ ἡ πρώτη αὐτῶν εἶναι = τῷ Σανσκρ. ishus (βέλος), ἡ δὲ δευτέρα = τῷ Σανσκρ. vishas, visham, Λατ. vi-rus, δηλητήριον.)

French (Bailly abrégé)

1ἰοῦ (ὁ) :
plur. irrég. ἰά;
trait, javelot.
Étymologie: cf. skr. ishus, flèche.
2ἰοῦ (ὁ) :
1 venin;
2 rouille du fer, ou du cuivre, càd vert-de-gris.
Étymologie: p. *Ϝιός, cf. lat. virus.

English (Slater)

ῑός
   1 venom met. δύο δὲ γλαυκῶπες αὐτὸν δαιμόνων βουλαῖσιν ἐθρέψαντο δράκοντες ἀμεμφεῖ ἰῷ μελισσᾶν καδόμενοι i. e. honey (O. 6.47)

Spanish

veneno

English (Strong)

perhaps from eimi (to go) or hiemi (to send); rust (as if emitted by metals); also venom (as emitted by serpents): poison, rust.

English (Thayer)

ἰοῦ, ὁ (on its very uncertain derivation see Kreussler in Passow, under the word; Curtius, § 591; (Vanicek, p. 969));
1. poison (of animals): ἰός ἀσπίδων ὑπό τά χείλη αὐτῶν, the poison of asps is under their lips, spoken of men given to reviling and calumniating and thereby injuring others, γλῶσσα) μεστή ἰοῦ θανατηφόρου, Pindar down).
2. rust: Jeremiah 12,24); Theognis, Theocritus, Plato, Theophrastus, Polybius, Lucian, others).

Greek Monotonic

ἰός: [ῑ], ὁ, πληθ. ἰοί, επίσης ἰά·
I. βέλος, σε Ομήρ. Ιλ., Τραγ.
II. 1. σκουριά, ιδίως του σιδήρου ή του χαλκού, σε Θέογν., Πλάτ.
2. δηλητήριο, λέγεται για τα φίδια, σε Τραγ.

Russian (Dvoretsky)

ἰός: I (ῑ) ὁ (эп. pl. тж. ἰά) дротик, преимущ. стрела (χαλκήρης, πτερόεις Hom.; ἀπὸ θώμιγγος ἰοὶ προσπίτνοντες Aesch.; πτηνοῖς ἰοῖς θηροβολεῖν Soph.; εἴργειν τινὰ ἰοῖς Eur.).
II (ῑ) ὁ
1) яд (ἐχιδνης Soph.; δρακόντων Eur.; ἐνίων θηρίων Plut.; θανατηφόρος NT);
2) сок: ἰ. μελισσῶν Pind. пчелиный сок, т. е. мед.
III (ῑ) ὁ ржавчина (χαλκοῦ καὶ σιδήρου Plat.; ἰοῦ χρῶμα Arst.; χρυσοῦ καὶ ἀργύρου NT).

Frisk Etymological English

1. Meaning: one and the same
See also: s. ἴα.
2.
Grammatical information: m.
Meaning: arrow (Il.; Trümpy Fachausdrücke 67).
Other forms: pl. ἰοί, also ἰά (Υ 68; on the change of genus Schwyzer-Debrunner 37)
Compounds: As 1. member e. g. in ἰο-δόκος receiving arrows (φαρέτρη Hom.), -η f. quiver (A. R.); on ἰο-χέαιρα s. v.
Origin: IE [Indo-European] [301] *isu- arrow
Etymology: From *ἰσϜ-ο- and except for the thematic vowel (Schwyzer 472) identical with Skt. íṣu-, Av. išu- arrow (Curtius 402; further lit. in Bq). Meier-Brügger, MSS 49 (19880 75-77, takes ι᾽ά as ntr. pl. from *ιhυ, and ἰός as a sec. sg. derived from it.
3.
Grammatical information: m.
Meaning: poison (Pi., trag., Plu.).
Compounds: As 1. member e. g. in ἰο-βόρος poison eating (Nic., Opp.);
Derivatives: ἰώδης poisonous (Rom. empire).
Origin: IE [Indo-European] [1134] *uiso- or *uiso-, *uiHso-? fluidity, slime, poison
Etymology: Old word for poison, often replaced by euphemistic expressions (φάρμακον, Lat. venēnum, Germ. gift, French poison etc.), but still present in the languages of the margin, i. e. Indo-Iranian and Italo-Celtic: Skt. viṣá- n., Av. vīša-, Lat. vīrus n. (genus sec.) = Irisch fī, IE *u̯īso-; on the quantity cf. e. g. the cases in Fraenkel Nom. ag. 1, 91. Beside these thematic forms there is Av. viš- id. and, with deviating meaning, Skt. viṣ- faeces. Thus Lat. vīrus also means tough fluidity, slime, sap; cf. also Welsh gwyar blood and 4. ἰός. As IE *u̯īs(o)- is prob. partly a tabuistic substitution, one considered connection with a verb, Skt. veṣati flow out (gramm.), with a Germ. river-name as Wisura Weser, Vistula Weichsel (Krahe Beitr. z. Namenforschung 4, 38ff.); however, these Old European river names of Krahe are in general pre-, i.e. non-IE. - Lit. bei Bq, WP. 1, 243f., W.-Hofmann s. vīrus.
4.
Grammatical information: m.
Meaning: rust on iron, verdigris on copper, bronze (Thgn., Hp., Pl., Theoc., SIG 284, 15 [Chios IVa]).
Derivatives: ἰώδης rust-coloured (Hp., Thphr.).
Origin: XX [etym. unknown]
Etymology: Given the changing meaning of IE *u̯īs(o)- (s. on 3. ἰός) our word has been identified with it (Fick 23, 242). It could be due to different uses according to occupation; note, that ἰός rust as opposed to ἰός poison was used also in prose, what may point to a stilistic differentiation.