1. the quality or state of being thin in width or thickness
2. the quality or state of having little body fat; leanness
3. the quality of being sparse or not dense

Examples

• The thinness of the paper made it easy to tear.
• Her extreme thinness worried her family and friends.
• The thinness of the mountain air made breathing difficult.
• The thinness of his excuse was obvious to everyone.
• The ice’s dangerous thinness prevented skating on the pond.
• The thinness of the crowd disappointed the performers.
• The fabric’s thinness made it perfect for summer clothing.