Quick Definition
I preserve, keep safe, keep in mind
Strong's Definition
to keep closely together, i.e. (by implication) to conserve (from ruin); mentally, to remember (and obey)
Derivation: from G4862 (σύν) and G5083 (τηρέω);
KJV Usage: keep, observe, preserve
Thayer's Greek Lexicon
συντηρέω, συντήρω: imperfect 3 person singular συνετήρει; present passive 3 person plural συντηροῦνται; (from Aristotle, de plant. 1, 1, p. 816a, 8 down);
a. to preserve (a thing from perishing or being lost): τί, passive (opposed to ἀπολλυσθαι), Mat_9:17; Luk_5:38 (T WH omit; Tr brackets the clause); τινα, to guard one, keep him safe, from a plot, Mar_6:20 (ἑαυτόν ἀναμάρτητον, 2Ma_12:42 (cf. Tob_1:11; Sir_13:12)).
b. to keep within oneself, keep in mind (a thing, lest it be forgotten (cf. σύν, II. 4)): πάντα τά ῤήματα, Luk_2:19 (τό ῤῆμα ἐν τῇ καρδία μου, Dan_7:28, Theod.; τήν γνώμην παῥ ἑαυτό, Polybius 31, 6, 5; (absolutely, Sir_39:2)).
Mounce Concise Greek Dictionary
συντηρέω syntēreō 3x
to keep safe and sound, Mat_9:17 ;
to observe strictly, or, to secure from harm, protect, Mar_6:20 ;
to preserve in memory, keep carefully in mind, Luk_2:19
Abbott-Smith Greek Lexicon
συν -τηρέω , -ῶ ,
[in LXX : Eze_18:19 ( H8104 ), Da TH Dan_7:28 A ( H5202 ), Sir_13:12 and freq ., Tob_1:11 , 2Ma_12:42 , al. ;]
"perfective" of τηρέω ( v. M , Pr., 113, 116),
to preserve, keep safe, keep close: c . acc pers ., Mar_6:20 ; c . acc rei , Mat_9:17 ; ἐν τ . καρδίᾳ , Luk_2:19 ( Arist . and later writers; cf. MM , xxiv).†
Moulton & Milligan — Vocabulary of the Greek NT
συντηρέω [page 614]
For this perfective of τηρέω ( Proleg . pp. 113, 116) = keep safe (I) c. acc. pers., as in Mar_6:20 , cf. P Tebt II. 416 .14 (iii/A.D.) πᾶν ποίησον συντηρῆσαι τὴν γυναῖκά μου ἕως παραγένομε ( l . παραγένωμαι ), do everything possible to protect my wife until I arrive (Edd.), P Oxy XII. 1418 .5 (A.D. 247) σ ]υντηρῆσαι τὸν παῖδα , and the iv/A.D. Gnostic charm ib . VI. 924 .1 ῆ̣̔ μ̣ὴ̣ν̣ φυλάξῃς καὶ συντηρήσῃς Ἀρίας ἀπὸ τοῦ ἐπιημερινοῦ φρικός , verily guard and protect Aria from ague by day : and (2) c. acc. rei, as in Mat_9:7 , cf. P Bouriant 10 .12 (B.C. 88) καλῶς ποιήσεις συντηρῶν τὸν τόπον , BGU IV. 1074 .2 (A.D. 275) τὰ δὲ [ὑ̣ ]πὸ το [ῦ ] δ̣[ὲ τ ]οῦ Σεβαστοῦ δ [εδ ]ομένα ὑμῖν νόμιμα καὶ φιλάνθ [ρ ]ωπα συντηρῶ , I keep safe the laws and privileges granted to you by Augustus, and Syll 930 (= .3 705) (B.C. 112) συντηρῆσαι τὰ ἐκ παλαιῶν χρόνων δεδομένα τίμια καὶ φιλάνθρωπα : see also ib . 655 (= .3 820) .8 (A.D. 83) μυστήρια ἀπὸ πλείστων ἐτῶν συντετηρημένα .
In P Tebt II. 282 .7 (late ii/B.C.) a guard declares that he will keep the best watch possible over other people s holdings φυ (λακὴν ) ἀλ [λο ]τρ [ί ]ων κλή (ρων ) συντηιρήσ̣ι̣ν ἀπὸ τ [ο ]ῦ βελτί <σ >του , and in BGU I. 180 .13 (ii/iii A.D.) a veteran claims that in view of his long military service, exemption from public burdens ought to be strictly observed in his case ἐπ᾽ ἐμοῦ συντηρεῖσθαι ὀφείλι . Cf. also ib . IV. 1106 .31 (B.C. 13) ἅ τε ἐὰν λάβῃ ἢ πιστευθῇ σῶα συντηρήσιν (= ειν ), and ib . 1126 .13 (B.C. 8), and for the subst. συντηρεία (not in LS 8 ) cf. Syll 932 (= .3 880) .52 (A.D. 202) συν [τηρ ]είας βουγαρίων .
Liddell-Scott — Intermediate Greek Lexicon
συντηρέω fut. ήσω "to preserve together": Pass., NTest. "to watch one's opportunity", Plut.
STEPBible — Tyndale Abridged Greek Lexicon
συν-τηρέω, -ῶ
[in LXX: Eze.18:19 (שָׁמַר), Da TH Dan.7:28 A (נְטַר), Sir.13:12 and freq., Tob.1:11, 2Ma.12:42, al. ;]
"perfective" of τηρέω (see M, Pr., 113, 116),
to preserve, keep safe, keep close: with accusative of person(s), Mrk.6:20; with accusative of thing(s), Mat.9:17; ἐν τ. καρδίᾳ, Luk.2:19 (Arist. and later writers; cf. MM, xxiv).†
(AS)