dia, intensive, and bebaioo, to confirm, make sure, denotes to assert strongly, "affirm confidently," 1 Timothy 1:7; Titus 3:8 (AV, "affirm constantly").

2: διϊσχυρίζομαι

(Strong's #1340 — Verb — diischurizomai — dee-is-khoo-rid'-zom-ahee )

as in No. 1, and ischurizosai, "to corroborate" (ischuros "strong;" see ABILITY , A, No. 2 and C, No. 2 note), primarily signifies "to lean upon," hence, "to affirm stoutly, assert vehemently," Luke 22:59; Acts 12:15 .

3: φάσκω

(Strong's #5335 — Verb — phasko — fas'-ko )

a frequentative form of the verb phemi (No. 4), denotes "to allege, to affirm by way of alleging or professing," Acts 24:9 (RV, "affirming," AV, "saying"); 25:19; Romans 1:22 , "professing." Some mss. have it in Revelation 2:2 , instead of the verb lego, "to say." See PROFESS , SAY.

4: φημί

(Strong's #5346 — Verb — phemi — fay-mee' )

"to say" (primarily by way of enlightening, explaining), is rendered "affirm" in Romans 3:8 . See SAY.

Bibliography Information
Vines, W. E., M. A. Entry for 'Affirm'. Vine's Expository Dictionary of NT Words. https://www.studylight.org/dictionaries/eng/ved/a/affirm.html. 1940.

Bible Dictionaries Affirm

Vine's Expository Dictionary of NT Words

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Affirm