Eight, Eighteen, Eighth
“eight” (Lat., octo, octavus; cp. Eng., “octagon,” “octave,” “octavo,” “October,” etc.), is used in Luk 2:21; Luk 9:28; Joh 20:26; Act 9:33; Act 25:6; 1Pe 3:20; in composition with other numerals, okto kai deka, lit., “eight and ten, eighteen,” Luk 13:4, Luk 13:11, Luk 13:16; triakonta kai okto, “thirty and eight,” Joh 5:5.
“eighth” (connected with the preceding), is used in Luk 1:59; Act 7:8; 2Pe 2:5; Rev 17:11; Rev 21:20.
an adjective, signifying an “eighth-day” person or thing, “eight days old” (okto, and hemera, “a day”), is used in Phi 3:5. This, and similar numerical adjectives not found in the NT, indicate duration rather than intervals. The Apostle shows by his being an “eighth-day” person as to circumcision, that his parents were neither Ishmaelites (circumcised in their thirteenth year) nor other Gentiles, converted to Judaism (circumcised on becoming Jews).