What it means
An affidavit is a formal written statement of the facts you want to rely on in a legal case. You sign it in front of an authorised witness (such as a lawyer or Justice of the Peace) and swear an oath, or make an affirmation, that its contents are true. Because it is sworn evidence, knowingly including false information in an affidavit can amount to perjury, a criminal offence. Affidavits are used heavily in family law and civil litigation, where much of the evidence is presented in writing rather than spoken aloud in the witness box.
How it's used
In her divorce application, Sarah filed an affidavit setting out the date she and her husband separated and the arrangements for their children.