Reentrant tuning

Reentrant tuning is a tuning of a stringed instrument in which the strings, or the courses), are not arranged in a continuous order from lowest pitch to highest pitch or from highest to lowest. Instead, at least one string is tuned to a pitch that breaks the otherwise ascending or descending sequence; this discontinuity is known as a re-entry.

Most re-entrant tunings contain only one re-entry. For example, in the ukulele the re-entry occurs between the third and fourth strings, whereas in the Venezuelan cuatro it occurs between the first and second strings.