Vertucci’s Classification System of Root canal System | Endodontics 

Vertucci has classified root canal configuration of human permanent teeth into eight types
Type 1 (1) -A single canal extends from the pulp chamber to the apex.
Type II (2-1) -two separate canals leave the pulp chamber and join short of the apex to form one canal.
Type III (1-2-1) -One canal leaves the pulp chamber, divides into two within the root, and then merges to exit as one canal.
Type IV (2) -Two separate and distinct canals extend from the pulp chamber to the apex.
Type V (1-2) -One canal leaves the pulp chamber and divides short of the apex into two separate and distinct canals with separate apical foramina.
Type VI (2-1-2) -Two separate canals leave the pulp chamber, merge within the body of the root, and re-divide short of the apex to exit as two distinct canals.
Type VII (1-2-1-2) -One canal leaves the pulp chamber, divides and then rejoins within the body of the root, and finally re-divides into two distinct canals short of the apex.
Type VIII (3) - Three separate canals extend from the pulp chamber to the apex.