1: ἀναγκαῖος
(Strong's #316 — Adjective — anankaios — an-ang-kah'-yos )

"necessary" (from ananke, "necessity;" see below), is so rendered in Acts 13:46; 1—Corinthians 12:22; 2—Corinthians 9:5; Philippians 2:25; Titus 3:14; Hebrews 8:3 , RV (AV, "of necessity"); for Acts 10:24 , "near friends," see NEAR , B.

2: ἀνάγκη
(Strong's #318 — Noun Feminine — ananke — an-ang-kay' )

"a necessity" (see No. 1), is rendered "(it was) necessary" in Hebrews 9:23 , lit., "it was a necessity." See DISTRESS , A, No. 1.

3: ἐπάναγκες
(Strong's #1876 — Adjective Neuter — epanankes — ep-an'-ang-kes )

an adjective akin to the preceding, with epi, used intensively, found only in the neuter form, is used as an adverb signifying "of necessity" and translated as an adjective in Acts 15:28 , "necessary," lit., "(things) of necessity."

Acts 28:10 NEED