A fingerprint is an impression of the friction ridges of all or any part of the finger.
A friction ridge is a raised portion of the epidermis on the palmar (palm and fingers) or plantar (sole and toes) skin, consisting of one or more connected ridge units of friction ridge skin.
These ridges are sometimes known as "dermal ridges" or "dermal papillae".
Fingerprint identification (sometimes referred to as dactyloscopy) is the process of comparing questioned and known friction skin ridge impressions (see Minutiae) from fingers, palms, and toes to determine if the impressions are from the same finger (or palm, toe, etc.).
The flexibility of friction ridge skin means that no two finger or palm prints are ever exactly alike (never identical in every detail), even two impressions recorded immediately after each other.
Fingerprint identification (also referred to as individualization) occurs when an expert (or an expert computer system operating under threshold scoring rules) determines that two friction ridge impressions originated from the same finger or palm (or toe, sole) to the exclusion of all others.