A biometric modality is a category of a biometric system depending upon the type of human trait it takes as input. Biometric modalities include fingerprint, face, iris, voice, hand writer recognition, and hand geometry.
The biometrics is largely statistical, there is not one biometric modality that is best for all implementations, and many factors must be taken into account when implementing a biometric device, including location, security risks, task (identification or verification), expected number of users, user circumstances, existing data, etc.. The more the data available from sample, the more the system is likely to be unique and reliable. It can work on various modalities pertaining to measurements of individual’s body and features, and behavioral patterns. The modalities are classified based on the person’s biological traits.