1.to know, εὖ οἶδα I know well; εὖ ἴσθι be assured: often c. acc. rei, νοήματα οἶδε, μήδεα οἶδε he is versed in counsels, Hom.; with neut. Adjs., πεπνυμένα, φίλα, ἀθεμίστια εἰδώς id=Hom.; also c. gen., τόξων εὖ εἰδώς cunning in the use of the bow; οἰωνῶν σάφα εἰδώς Od.: —χάριν εἰδέναι τινί to acknowledge a debt to another, thank him, Il., etc.:—the Imperat. in protestations, ἴστω Ζεὺς αὐτός be Zeus my witness, id=Il.; doric ἴττω Ζεύς, ἴττω Ar.: —εἰδώς absol. one who knows, εἰδυίηι πάντ᾽ ἀγορεύω Il.; ἰδυίηισι πραπίδεσσι with knowing mind, id=Il.
2.c. inf. to know how to do, id=Il., attic
3.with the part. to know that so and so is the case, ἴσθι μοι δώσων know that thou wilt give, Aesch.; τὸν Μῆδον ἴσμεν ἐλθόντα Thuc.