Lexical Definition

‎φυλακή‎ phylakḗ (foo-lak-ay') prison/watch: prison ^G:N-F
from ‎φυλάσσω‎

cage, hold, (im-)prison(-ment), ward, watch.

• a guarding or (concretely, guard), the act, the person
• figuratively, the place, the condition, or (specially), the time (as a division of day or night), literally or figuratively

Abbott-Smith

φυλακή, -ῆς, ἡ (< φυλάσσω) [in LXX chiefly for מִשְׁמֶרֶת and cogn. forms, also for כֶּלֶא etc. ;]
(a) actively, a guarding, guard, watch (Hom., Plat., Xen., al.): cogn. acc., φυλάσσειν φυλακάς, to keep watch, Lk 2:8;
(b) of those who keep watch (as also Lat. custodia), a guard; pl., sentinels, a guard (Hom., al.): Ac 12:10;
(c) of the place where persons are kept under guard, a prison (Hdt., Thuc., al.): Mt 14:10, Mk 6:17, Lk 3:20, Ac 5:19, II Co 6:5, I Pe 3:19, Re 18:2, al.;
(d) of the time during which guard was kept by night (Lat. vigilia; Anthol.), a watch: Mt 14:25 24:43, Mk 6:48, Lk 12:38

Abbott-Smith References

Liddell-Scott-Jones

φυλακή-ή, ἡ,

(φύλαξ) watching or guarding, especially by night, φυλακῆς μνήσασθε [Refs 8th c.BC+]; φυλακὰς ἔχειν keep watch and ward, [Refs]; φ. κατέχειν [Refs 5th c.BC+]; φυλακὴ ἔχει αὐτόν watching engages him, variant in [Refs 8th c.BC+] tell an unarmed man to stand on the defensive, i.e. to give commands that cannot be obeyed, [Refs 5th c.BC+]; ὅπως ἀφανὴς εἴη ἡ φ. that there might be nothing visible to watch, [Refs 5th c.BC+]; φυλακὰς φυλάξειν keep watch and ward, [Refs 5th c.BC+]; φυλακὰς καταστήσασθαι, κατασκευάσασθαι, [Refs 5th c.BC+]

__2 watch or guard, of persons, [NT+5th c.BC+]; φ. τοῦ σώματος a body guard, [Refs 5th c.BC+], etc.; garrison of a place or fortress, [Refs 5th c.BC+]; ἡ ἐν τῇ Ναυπάκτῳ φ., of a squadron of ships, [Refs 5th c.BC+]
__2.b the rank of φύλακες, [Refs 5th c.BC+]
__3 station, post, [Refs 8th c.BC+]; Διὸς φ., [Refs 4th c.BC+] name for the centre of the universe, [Refs 4th c.BC+]
__4 of time, a watch of the night, ἐπεὰν τῆς νυκτὸς ἦ δευτέρη φ. [Refs 5th c.BC+]; πρώτης φ. ἀρχομένης Wilcken [Refs 3rd c.BC+]; φυλακαῖσι νυκτέροισιν [Refs 5th c.BC+]: of these there were three, accusative to [Refs 5th c.BC+]; but five are mentioned in [Refs 7th c.BC+]; and the Roman division was four, [NT]
__5 place for keeping others in, ward, prison, δημοσία φ. [NT+1st c.BC+]; πολιτικὴ φ. the town-prison, [Refs 1st c.AD+]
__6 Astrology texts ={ταπείνωμα}, [Refs]
__II guarding, keeping, preserving, whether for security or custody, ἐν φυλακῇ ἔχειν τινά [Refs 5th c.BC+]; τὸν Ἰσθμὸν ἔχειν ἐν φ. to keep the Isthmus guarded or occupied, [Refs]; τὸν ἠνείκαντο γλώσσης χαρακτῆρα τοῦτον ἔχειν ἐν φ. to preserve the same character of language, [Refs 6th c.BC+]; στόματος φυλακᾷ κατασχεῖν φθόγγον probably in [Refs 4th c.BC+]; ἐν φ. σχεθέμεν μεγάλᾳ be very ware of, [Refs 5th c.BC+]; φυλακὴν ἔχειν, ={φυλάττεσθαι}, keep guard, be on the watch, περί τινα [Refs 5th c.BC+]; φ. ἔχειν μή.. [Refs 5th c.BC+]; φ. λαμβάνειν μή.. [Refs 4th c.BC+]; δεινῶς ἦσαν ἐν φυλακῇσι were straitly on their guard, [Refs 5th c.BC+]
__II.2 custody of property, [Refs 4th c.BC+]
__II.3 safeguard, τὴν μεγίστην φ. ἀνῄρηκε τῆς πόλεως its chief safeguard, [Refs 5th c.BC+]; δημοκρατίας, μοναρχίας φ., [Refs 5th c.BC+]
__III (from middle) precaution, πολλῆς φ. ἔργον [Refs 5th c.BC+]
__III.2 with genitive, precaution against, εὐλάβεια φ. κακοῦ [Refs 5th c.BC+]

_{LSJ Scripture Refs: Acts.12.10 ☩ Matt.14.25 ☩ Matt.18.30 ☩ LXX.Gen.40.3 ☩ Matt.14.3}