A). like ὅτε , exc. that the sense is less definite (cf. X. Cyr. 1.6.3 ), though the two were freq. used without distinction :

I). Relat., with the ind., mostly with reference to the past, when, Il. 1.399 , 3.173 , etc.; the ind. ἦστε is omitted, 8.230 : in Class. Att. Prose only ὅτε is so used, when referring to a particular time, but later ὁπότε returns, as ὁπότε περιῆν when she was alive, POxy. 243.10 (i A. D.): with the pres. in a simile, ὡς δ’ ὁπότε .. ποταμὸς πεδίονδε κάτεισι Il. 11.492 : with subj., like ὁπόταν , with reference to an indef. number of occasions in the pres. or to the future, ὁππότ’ Ἀχαιοὶ Τρώων ἐκπέρσωσ’ εὖ ναιόμενον πτολίεθρον 1.163 , cf. 13.817 , 21.112 , Od. 14.170 , Hes. Th. 782 : sts. in similes, ὡς ὁπότε νέφεα Ζέφυρος στυφελίξῃ Il. 11.305 , cf. Od. 4.335 ; but ὁπότ’ ἄν, Ep. ὁπότε or ὁππότε κεν, is more common with subj., and in Att. Prose ἄν must be used, v. ὁπόταν : Cyrenaic ὁπόκα κα δήληται Berl.Sitzb. l. c.

2). with opt.:

a). to express an event that occurred often, ὁπότε Κρήτηθεν ἵκοιτο Il. 3.233 , cf. 10.189 , 15.284 , Od. 11.591 , Th. 1.99 , 2.15 , Pl. Smp. 220a , X. An. 3.4.28 .

b). after a verb of waiting, of a time future relatively to the past, ἷζε .. δέγμενος ὁππότε ναῦφιν ἀφορμηθεῖεν Il. 2.794 , cf. 4.334 , 7.415 , 9.191 , 18.524 .

c). in orat. obliq., S. Tr. 824 (lyr.), X. An. 4.6.20 ; in implied orat. obliq., Od. 24.344 (of a past promise); ἀποδοτέον .. ὁ. μανεὶς ἀπαιτοῖ we were not [as you remember] to .. , Pl. R. 332a .

d). where the principal clause has an opt., μηδ’ ἀντιάσειας ἐκείνῳ ὁππότε νοστήσειε Od. 18.148 , cf. Pl. R. 396c , X. Cyr. 1.6.3 .

II). in indirect questions, with ind., ἦ ῥά τι ἴδμεν .. ὁππότε Τηλέμαχος νεῖται; when he is to return, Od. 4.633 ; εἰς ὁ. by what time, Aeschin. 3.99 : rarely after a past tense, προσεδέρκετο, δέγμενος αἰεί, ὁππότε δὴ .. ἐφήσει (for ἐφείη, v. supr. 1.2 b) Od. 20.386 ; εἰς σὲ βλέψαι καὶ τὸν ταμίαν ὁπότ’ ἄριστον παραθήσει Ar. V. 613 .

III). ὁποτεοῦν at any time whatever, Arist. Metaph. 1049a1 .

B). in causal sense, because, since, with ind., Thgn. 749 (s. v.l.), Hdt. 2.125 , Pl. Lg. 895c , etc.; also ὁπότε γε S. OC 1699 (lyr.), X. Cyr. 8.3.7 .