A — 1: νηστεία
(Strong's #3521 — Noun Feminine — nesteia — nace-ti'-ah )

"a fasting, fast" (from ne, a negative prefix, and esthio, "to eat"), is used (a) of voluntary abstinence from food, Luke 2:37; Acts 14:23 (some mss. have it in Matthew 17:21; Mark 9:29 ); "fasting" had become a common practice among Jews, and was continued among Christians; in Acts 27:9 "the Fast" refers to the Day of Atonement, Leviticus 16:29; that time of the year would be one of dangerous sailing; (b) of involuntary abstinence (perhaps voluntary is included), consequent upon trying circumstances, 2—Corinthians 6:5; 11:27 .

A — 2: νῆστις
(Strong's #3523 — Noun Feminine — nestis — nace'-tis )

"not eating" (see No. 1), "fasting," is used of lack of food, Matthew 15:32; Mark 8:3 .

Acts 27:21ABSTINENCE
B — 1: νηστεύω
(Strong's #3522 — Verb — nesteuo — nace-tyoo'-o )

"to fast, to abstain from eating" (akin to A, Nos. 1 and 2), is used of voluntary "fasting," Matthew 4:2; 6:16,17,18; 9:14,15; Mark 2:18,19,20; Luke 5:33,34,35; 18:12; Acts 13:2,3 . Some of these passages show that teachers to whom scholars or disciples were attached gave them special instructions as to "fasting." Christ taught the need of purity and simplicity of motive.

Matthew 9:15Zechariah 8:19Acts 10:30
C — 1: ἄσιτος
(Strong's #777 — Adjective — asitos — as'-ee-tos )

"without food" (a, negative, sitos, "corn, food"), is used in Acts 27:33 , "fasting." Cp. asitia, Note under A, No. 2.