A friend is one who rejoices in our good and grieves for our pain, and this purely on our own account.

[τούτων δὲ ὑποκειμένων ἀνάγκη φίλον εἶναι τὸν συνηδόμενον τοῖς ἀγαθοῖς καὶ συναλγοῦντα τοῖς λυπηροῖς μὴ διά τι ἕτερον ἀλλὰ δι᾽ ἐκεῖνον.]

Aristotle (384-322 BC) Greek philosopher

Rhetoric [Ῥητορική; Ars Rhetorica], Book 2, ch. 4, sec. 3 (2.4.3) / 1381a (350 BC) [tr. Jebb (1873)]
    (Source)

(Source (Greek)). Alternate translations:

• "He who rejoices with one in prosperity, and sympathises with one in pain, not with a view to anything else but for his friend's sake, is a friend." [Source (1847)]


• "One who participates in another's joy at good fortune, and in his sorry at what aggrieves him, not from any other motive, but simply for his sake, is his friend." [tr. Buckley (1850)]


• "Your friend is the sort of man who shares your pleasure in what is good and your pain in what is unpleasant, for your sake and for no other reason." [tr. Roberts (1924)]


• "He is a friend who shares our joy in good fortune and our sorrow in affliction, for our own sake and not for any other reason." [tr. Freese (1926)]


• "The following people are our friends: those who share our pleasure when good things happen and our distress when bad things happen for no other reason than for our sake." [tr. Waterfield (2018)]


• "A friend is one who shares in the other fellow's pleasure at the good things and his pain at what is grievous, for no other reason than that fellow's sake." [tr. Bartlett (2019)]


• "A friend is someone who is a partner in our happiness and a partner in our sorrow not for any other reason but for friendship." [tr. @sentantiq (2019)]