Lexical Definition

‎φρήν‎ phrḗn (frane) thinking ^G:N-F
probably from an obsolete (to rein in or curb; compare ‎φράσσω‎)

understanding.

• the midrif (as a partition of the body), i.e. (figuratively and by implication, of sympathy) the feelings (or sensitive nature
• by extension (also in the plural) the mind or cognitive faculties)

Abbott-Smith

φρήν gen., φρενός, ἡ, [in LXX most freq. in Pr (6:32, al.) and chiefly for לֵב; also III Mac 4:16 5:47 ;]
chiefly in Hom. and Trag., but also in Plat., al., both sing. and pl.;
1. in physical sense, the parts about the heart, midriff.
2. heart, mind, thought: pl., I Co 14:20 (v. Edwards, Eng.-Gr. Lex., App., 1).†

Abbott-Smith References

Liddell-Scott-Jones

φρήν, ἡ,

genitive φρενός, plural φρένες, genitive φρενῶν, dative φρεσί: older dative plural φρασί (ν) [Refs 6th c.BC+]:

__I midriff, κραδία φρένα λακτίζει [Refs 4th c.BC+]; elsewhere always in plural, ἔνθα φρένες ἔρχαται ἀμφ᾽ ἁδινὸν κῆρ [Refs 8th c.BC+]; τὰς φρένας διάφραγμα εἰς τὸ μέσον αὐτῶν (i.e. τοῦ θώρακος καὶ τοῦ κύτους) τιθέντες [Refs 8th c.BC+]
__I.2 heart, as seat of the passions, e.g. of fear, τρομέοντο δέ οἱ φρένες ἐντός [Refs 8th c.BC+]; of joy and grief, φρένα τέρπεσθαι φόρμιγγι [Refs]; of anger, [Refs 8th c.BC+]; of courage, ἕνα φρεσὶ θυμὸν ἔχοντες [Refs 8th c.BC+], etc.; of bodily appetites, such as hunger, etc., [Refs]: the shades of the dead are without it, ψυχὴ καὶ εἴδωλον, ἀτὰρ φρένες οὐκ ἔνι πάμπαν [Refs] (except the shade of Teiresias, [Refs 8th c.BC+]: so generally in Poets, φρενὸς ἔνδοθεν ἄλγεα κεῖται [Refs 6th c.BC+]; ἐκ φρενός from one's very heart, ὁ ἐκ φρενὸς λόγος a sincere speech, [Refs]; οὐκ ἀπ᾽ ἄκρας φρενός not superficially and carelessly, [Refs]; φῦσαι φρένας to produce a haughty spirit, [Refs 5th c.BC+]
__I.3 mind, as seat of the mental faculties, perception, thought, ἔγνω ᾗσιν ἐνὶ φ. [Refs 8th c.BC+]; μετὰ φρεσὶ μερμηρίξαι, βάλλεσθαι, [Refs 8th c.BC+]; τῷ γὰρ ἐπὶ φρεσί θῆκε put in his mind, suggested it,[Refs]; ἐπιγνάμπτει φρένας (variant for{νόον}) ἐσθλῶν [φρήν 10.45 ">Refs]; ἀνὴρ φρένας ἀφνειός rich (only) in his imagination, [Refs 8th c.BC+]; ὀρθᾷ, ἐλευθέρᾳ φρενί, [Refs 8th c.BC+]: plural, wits, Κύκλωπα περὶ φρένας ἤλυθε οἶνος [Refs 8th c.BC+]: of losing one's wits, φρενῶν ἀφεστάναι, ἐκστῆναι, μεθεστάναι, [Refs 5th c.BC+]; ἔξεδροι, παράκοποι, [Refs 5th c.BC+]; of persons in their senses, ἐπήβολος φρενῶν [Refs 5th c.BC+] (so in later Prose, οἱ φρένας ἔχοντες [Refs 5th c.BC+]; φρένες, opposed to σῶμα, [Refs 5th c.BC+]; attributed to animals, μετὰ φρεσὶ γίγνεται ἀλκή [Refs 8th c.BC+]—The word is not common in early Prose, τίς αὐτῶν νόος ἢ φρή; [Refs 1st c.AD+]; συμφορὰ τῶν φ., i.e. madness, [Refs 5th c.BC+]
__I.4 will, purpose, οὔ τι Διὸς βέομαι φρεσίν [Refs 8th c.BC+].—In usage there is little or no distinction observable between singular and plural, but the singular is not found in Prose (except [Refs 5th c.BC+]