False acceptance Rate (FAR) describe the amount of false recognition..
In biometrics, the instance of a security system incorrectly verifying or identifying an unauthorized person. Also referred to as a type II error (see error type), a false acceptance typically is considered the most serious of biometric security errors as it gives unauthorized users access to systems that expressly are trying to keep them out.
The false acceptance rate, or FAR, is the measure of the likelihood that the biometric security system will incorrectly accept an access attempt by an unauthorized user. A system’s FAR typically is stated as the ratio of the number of false acceptances divided by the number of identification attempts.