Which biometric feature is considered unique to each individual?

Fingerprints are considered unique to each individual because they are formed in the womb and remain unchanged throughout a person's life, except in rare cases of injury or severe skin diseases. The patterns created by the ridges and valleys of skin on a person's fingers are so distinct that even identical twins will have different fingerprints. This uniqueness makes fingerprints a reliable biometric feature for identification purposes.

In contrast, height, voice pitch, and hair color can vary greatly among individuals but are not exclusive. Height can be influenced by genetics and nutrition, voice pitch can change over time due to various factors such as age or health, and hair color can vary due to environmental factors or personal choices. These characteristics may show variation or similarity among individuals and do not serve as definitive identifiers like fingerprints do.