Personal Identification Number (PIN)

A password consisting only of decimal digits.
SOURCE: SP 800-63

A secret that a claimant memorizes and uses to authenticate his or her identity. PINs are generally only decimal digits.
SOURCE: FIPS 201

An alphanumeric code or password used to authenticate an identity.
SOURCE: FIPS 140-2

A short numeric code used to confirm identity.
SOURCE: CNSSI-4009