From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): (n.) A word or phrase expressing affirmation or assent; as, yes, that is so, etc.

(2): (a.) Positive; dogmatic.

(3): (a.) Confirmative; ratifying; as, an act affirmative of common law.

(4): (a.) That affirms; asserting that the fact is so; declaratory of what exists; answering "yes" to a question; - opposed to negative; as, an affirmative answer; an affirmative vote.

(5): (a.) Positive; - a term applied to quantities which are to be added, and opposed to negative, or such as are to be subtracted.

(6): (a.) Expressing the agreement of the two terms of a proposition.

(7): (n.) That which affirms as opposed to that which denies; an affirmative proposition; that side of question which affirms or maintains the proposition stated; - opposed to negative; as, there were forty votes in the affirmative, and ten in the negative.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

(Gr. Διαβεβαίομαι , Διϊσχυρίζομαι , etc.). Among the Jews the formula of assent or affirmation was כֵּן דַּבִּרְתָּ , Σὺ Εῖπας , Thou Hast Said, or Thou Hast Rightly Said. It is stated by Aryda and others that this is the prevailing mode in which a person expresses his assent, at this day, in Lebanon, especially when he does not wish to assert any thing in express terms. This explains the answer of our Savior to the high-priest Caiaphas ( Matthew 26:64), when he was asked whether he was the Christ, the son of God (see also  Matthew 26:25, and. comp.  John 18:37). Instances occur in the Talmud: thus, "A certain man was asked, Is Rabbi dead? He answered, Ye have said: on which they rent their clothes" taking it for granted from this answer that it was so (Jerusalem Talmud, Kilaim, 32, 2). All readers even of translations are familiar with a frequent elegancy of the Scriptures, or rather of the Hebrew language, in using an affirmative and negative together. by which the sense is rendered more emphatic: sometimes the negative first, as  Psalms 119:17, "I shall not die, but live," etc., sometimes the affirmative first, as  Isaiah 38:1, "Thou shalt die, and not live." In  John 1:20, there is a remarkable instance of emphasis produced by a negative being placed between two affirmatives, "And he confessed, and denied not, but confessed, I am not the Christ." (See Oath).