1: ἐκτός
(Strong's #1622 — Adverb — ektos — ek-tos' )

an adverb, lit., "outside," is used with ei me, as an extended conjunction signifying "except;" so in 1—Corinthians 14:5; in 1—Corinthians 15:2 , RV, for AV, "unless;" in 1—Timothy 5:19 , RV, for AV, "but." It has the force of a preposition in the sense of (a) "outside of," in 1—Corinthians 6:18 , "without;" in 2—Corinthians 12:2 , "out of;" (b) "besides," except, in Acts 26:22 , RV, "but," for AV, "other than;" in 1—Corinthians 15:27 "excepted." For its use as a noun see Matthew 26:26 , "(the) outside." See OTHER , OUT OF , OUTSIDE , UNLESS , WITHOUT.

2: παρεκτός
(Strong's #3924 — Adverb — parektos — par-ek-tos' )

a strengthened form of No. 1 (para, beside), is used (a) as an adverb, signifying "without," 2—Corinthians 11:28; lit., "the things without," i.e., the things happening without; (b) as a preposition signifying "except;" in Matthew 5:32 , "saving;" in Acts 26:29 , "except."

Matthew 19:9
3: πλήν
(Strong's #4133 — Adverb — plen — plane )

an adverb, most frequently signifying "yet, howbeit," or "only," sometimes has the meaning "except (that)," "save (that)," Acts 20:23; Philippians 1:18 , RV, "only that," for AV, "notwithstanding." It is also used as a preposition, signifying "except, save," Mark 12:32 , "but;" John 8:10 , "but" (AV only); Acts 8:1 , "except;" Acts 15:28 , "than," 27:22, "but (only)."