1. The property of an attractively thin person
   "His slightness made him look younger than his age";
   - slenderness, slimness
    
2. Slenderness
   "The slightness of the branch made it unsuitable for supporting the weight";
   - delicacy
    
3. The quality of being unimportant and petty or frivolous
   "The slightness of the evidence made the case weak";
   - pettiness, triviality, puniness

Type of: leanness, littleness, smallness, spareness, thinness, unimportance