asperity

n. vulgarity, coarseness; harshness, roughness

Asperity is defined as unevenness of surface, roughness, ruggedness (OED). Flat surfaces, even those polished to a mirror finish, are not truly flat on an atomic scale. They are rough, with sharp, rough or rugged outgrowth, termed asperities.When two macroscopically flat surfaces come into contact, initially they only touch at a few of these asperity points. These cover only a very small portion of the surface area. Friction and wear originate at these points and thus understanding their behavior is important when studying materials in contact. When the surfaces are subjected to a compressive load, the asperities plastically deform, increasing the contact area between the two surfaces until the contact area is sufficient to support the load.
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Noun
1. something hard to endure; "the asperity of northern winters"
(synonym) grimness, hardship, rigor, rigour, severity, rigorousness
(hypernym) difficulty, difficultness
2. harshness of manner
(synonym) sharpness
(hypernym) ill nature

(n.)
Sharpness; disagreeableness; difficulty.
  

(n.)
Roughness to the taste; sourness; tartness.
  

(n.)
Roughness or harshness of sound; that quality which grates upon the ear; raucity.
  

(n.)
Roughness of surface; unevenness; -- opposed to smoothness.
  

(n.)
Moral roughness; roughness of manner; severity; crabbedness; harshness; -- opposed to mildness.
  

n.
1. roughness of surface
کھردرا پن , ناہمواري , اونچان , نيچان
2. harshness of sound
رکھائي , سختي , کرختگي , اکھڑ پن
3. acrimony
تيزي , کڑواہٹ , تلخي ? ترشي
4. moroseness
روکھا پن , ترش روئي , بدمزاجي