What is a delta in fingerprint terminology?

In fingerprint terminology, a delta refers specifically to the triangular ridge patterns found in certain types of fingerprint designs. Deltas are important landmark features in ridge patterns, particularly in loop and whorl patterns. Recognizing and understanding deltas aids in the identification and classification of fingerprints during forensic analysis. They serve as reference points that help in determining how the ridges flow and can significantly assist in matching fingerprints to individuals.

The other choices describe different concepts that are not related to the definition of a delta. Visible fingerprints refer to prints that can be seen with the naked eye, a specific chemical used to develop prints relates to methods for revealing hidden fingerprints, and patent fingerprints are those that are left in a medium like ink or blood, both of which do not pertain to the triangular ridge pattern known as a delta.