1) Clause 2) Section 1) Section 2) Segment 3) Subdivision 
[n] - a section of a section
subdivision noun a section of a section; a part of a part; i.e., a part of something already divided
the small section within a bigger section of hair that you are working within. Subsectioning is key in keeping track of the hair that you have already cut and the hair that still needs cutting. Very important!
a part or division of a section.