What is Affirmation?

Legal Definition
Practice. A solemn declaration and asseveration, which a witness makes before an officer, competent to administer an oath in a like case, to tell the truth, as if be had been sworn.

2. In the United States, generally, all witnesses who declare themselves conscientiously scrupulous against taking a corporal oath, are permitted to make a solemn affirmation, and this in all cases, as well criminal as civil.

3. In England, laws have been enacted which partially relieve persons who, have conscientious scruples against taking an oath, and authorize them to make affirmation. In France, the laws which allow freedom of religious opinion, have received the liberal construction that all persons are to be sworn or affirmed according to the dictates of their consciences; and a quaker's affirmation has been received and held of the same effect as an oath. Merl. Quest. de Droit, mot Serment, 1.

4. The form is to this effect: "You, A B, do solemnly, sincerely, and truly declare and affirm," &c. For the violation of the truth in such case, the witness is subject to the punishment of perjury " as if he had been sworn.

5. Affirmation also means confirming; as, an affirmative statute.
-- Bouviers Law Dictionary
Legal Definition
In practice. A solemn and formal declaration or asseveration that an affidavit is true, that the witness will teli the truth, etc., this being substituted for an oath in certain cases. A solemn religious asseveration in the nature of an oath. 1 GreenL Ev. ยง 371.
-- Black's Law Dictionary
Legal Definition
A statement having the same effect and consequences as an oath, but not sworn to. See 18 Pick. (Mass.) 153.
-- Ballentine's Law Dictionary