25 Ἀναγκαῖον δὲ ἡγησάμην Ἐπαφρόδιτον τὸν ἀδελφὸν καὶ συνεργὸν καὶ συστρατιώτην μου, ὑμῶν δὲ ἀπόστολον καὶ λειτουργὸν τῆς χρείας μου, πέμψαι πρὸς ὑμᾶς, 26 ἐπειδὴ ἐπιποθῶν ἦν πάντας ὑμᾶς καὶ ἀδημονῶν, διότι ἠκούσατε ὅτι ἠσθένησεν. 27 καὶ γὰρ ἠσθένησεν παραπλήσιον θανάτῳ· ἀλλ᾽ ὁ θεὸς ἠλέησεν αὐτόν, οὐκ αὐτὸν δὲ μόνον ἀλλὰ καὶ ἐμέ, ἵνα μὴ λύπην ἐπὶ λύπην σχῶ.
25 Still, I considered it necessary to send to you Epaphroditus, brother and coworker and fellow-soldier of mine, and messenger from you and minister to my needs, 26 because he was longing for all of you and grieved because you heard that he was sick. 27 For indeed he was sick close to death; but God had mercy on him, and not only him but also me, that I might not have sorrow upon sorrow.
ἐπειδὴ, “since, because” is used 10 times in the NT. It is from ἐπί + εἰ + δή = “aptly if indeed”, i.e. Assuming a premise is factual, this is what will follow.
ἐπιποθέω “I long for, strain after, desire greatly” (9x in the NT) is from ἐπί (intensifier) + ποθεῶ, “yearn affectionately”. Thayer says ἐπί is directive, not intensive, i.e. it turns “I yearn” into “I yearn for (a person/thing)”. Other NT words from this root are the adjective ἐπιπόθητος, used in 4:1, and nouns ἡ ἐπιποθία (Rom. 15:23) and ἡ ἐπιπόθησις (2 Cor. 7:7, 11).
Some notable manuscripts have ἰδεῖν after πάντας ὑμᾶς, “longing to see you all”. EGGNT notes that the addition likely came about due to of the influence of Rom. 1:11, 1 Thess. 3:6, and 2 Tim. 1:4.
ἀδημονέω (3x in the NT), “I feel fear, lack courage, am distressed, troubled”, is perhaps from δῆμος, thus with the alpha primative originally meant “not at home”. Some suggest this means Epaphroditus was “homesick”, but EGGNT says this is reading too much into it.
ἀσθενέω, “I am weak”, is from ἀσθενής, alpha primitive + σθενος, “strength”. Along with cognate adjective ἀσθενής and noun ἡ ἀσθένεια, the word group is used in the NT about half of the time idiomatically to mean “I am sick”, “sick”, “sickness”.
παραπλήσιον, a NT hapax legomenon, literally means “alongside your neighbor”, thus “very close, nearly”.
ἡ λύπη (16x in the NT) is “pain, grief, sorrow, affliction, vexation”. The cognate verb λυπέω (“I grieve, vex”) is used 26x and so the root is worth memorizing.
Remember that the real root of ἔχω is σεχ, which comes out as σχ in perfect and aorist forms.