A written declaration upon oath made before an authorized official. A written statement that someone makes after promising officially to tell the truth.An affidavit can be used as proof in a law court. The term is pronounced as "afuhDAYvit. " Breaking it down: "af" as in "after," "uh" as in "umbrella," "DAY" with emphasis, and "vit" rhymes with "fit." This video shows you How to Pronounce Affidavit, pronunciation guide. AFFIDAVIT. North Carolina.