Learn in the textbookUser Authentication (Knowledge-Based and Possession-Based)
DefinitionMulti-factor authentication (多要素認証) confirms identity by combining two or more authentication factors (認証要素) of different types.
ExplanationThe possession factor is also called an owned item (所有物); the biometric factor covers behavioral traits like handwriting as well as physical ones like fingerprints and veins, and it also goes by the loanword biometrics (バイオメトリクス). Using two factors of different types and granting access only after both checks pass is called two-factor authentication (二要素認証). If one factor is broken, the other still stands, which makes the defense stronger.
AnalogyIt is like opening a bank safe-deposit box, where you must give a PIN at the counter and also turn your own key. Someone who learns the PIN still cannot open it without the key.
Memory hookMFA stands for multi-factor authentication, and a factor is one type of proof.