名詞 flatness:

1. the property of having two dimensions
   同義詞：two-dimensionality, planeness
2. a want of animation or brilliance
3. a deficiency in flavor
4. the property of having little or no contrast; lacking highlights or gloss
   同義詞：lusterlessness, lustrelessness, mat, matt, matte
5. inactivity; showing an unusual lack of energy
   同義詞：languor, lethargy, sluggishness, phlegm

1. Not a single tree relieved the flatness of the plain.
   平原上單調(diào)得毫無變化，連一棵樹都沒有。