The sweat glands in the skin of your fingertips produce a water-based oil solution that coats the ridges of your print. When your finger makes contact with a surface, this solution leaves behind a facsimile of your fingertip ridges called a latent print. Latent prints are what allow fingerprint reading devices to electronically scan and analyze your finger.

Fingerprint patterns are divided into the three main groups shown below.

Arch 5% of all prints

Loop 65% of all prints

Whorl 30% of all prints

Common Line Types Found in Fingerprints

The center area of the fingerprint containing the arch, loop, or whorl is called the pattern area. This area and its contents determine the classification of the print.

In addition to the predominant fingerprint shape, the pattern area also contains many different features called line types. The most common line types are illustrated below.

Line Type	Name	Description
	Arch	An arched line. Fingerprints made up primarily of arches are classified as arch prints.
	Bifurcation	The intersection of two or more converging or diverging line types.
	Ellipse	A circular or oval-shaped line generally found in the center of whorl patterns.
	Island	A line that stands alone. An island does not touch another line and is totally contained in the pattern area of interest.
	Loop	A curved line that begins and ends on the same axis.
	Rod	A straight line that is generally found in the center of the fingerprint pattern area.
	Spiral	A line that spirals out from the center of the fingerprint. Spirals are common to whorl patterns.
	Sweat gland	A sweat-producing gland in the fingertip. Every finger contains many sweat glands. The moisture that they produce allows fingerprints to be electronically imaged.
	Tented arch	An arch that quickly rises and falls at a steep angle.

Line types contain common micro-features called minutiae. Most fingerprint classification systems analyze the minutiae points of the fingerprint pattern. Some examples of minutiae are the intersections of bifurcations, the endpoints of islands, and the center points of sweat glands.