A precursor wave is a term mainly used in neuroscience to describe a membrane potential redistribution that precedes a larger, slower electrical potential change known as the primary wave. Synonyms for precursor wave can include "incipient potential", "early wave", "initial wave", or "trigger wave". Different areas of study may use different terminology to describe precursor waves, but they all share the core concept of an earlier, smaller, and faster wave that helps to initiate or propagate a larger response. Precursor waves can occur in various biological systems, including the retina, the spinal cord, and the brain. Understanding precursor waves and their characteristics can provide insights into the functioning and dysfunctioning of these systems.