1: πλοῖον
(Strong's #4143 — Noun Neuter — ploion — ploy'-on )

akin to pleo, "to sail," a boat or a ship, always rendered appropriately "boat" in the RV in the Gospels; "ship" in the Acts; elsewhere, James 3:4; Revelation 8:9; 18:17 (in some mss.),19. See BOAT , No. 2.

2: πλοιάριον
(Strong's #4142 — Noun Neuter — ploiarion — ploy-ar'-ee-on )

a diminutive form of No. 1, is translated "ship" in the AV of Mark 3:9; 4:36; John 21:8; "(took) shipping" in John 6:24 , AV, RV "(got into the) boats." See BOAT , No. 1.

3: ναῦς
(Strong's #3491 — Noun Feminine — naus — nowce )

denotes "a ship" (Lat. navis, Eng. "nautical," "naval," etc.), Acts 27:41 . Naus, in classical Greek the ordinary word for a "ship," survived in Hellenistic Greek only as a literary word, but disappeared from popular speech (Moulton, Proleg., p. 25). Blass (Philology of the Gospels, p. 186) thinks the solitary Lucan use of naus was due to a reminiscence of the Homeric phrase for beaching a "ship."

Acts 21:6TAKE