hairline (n.)

• band
• bar
• dash
• delicacy
• delineation
• diagonal
• differentia
• differential
• distinction
• hachure
• hairsplitting
• hatching
• line
• lineation
• margin
• nice
• nicety
• nuance
• refinement
• score
• slash
• streak
• striation
• strip
• stripe
• striping
• stroke
• subtlety
• underline
• underscore
• virgule