what is the definition of impurity??

Answer 1

Any substance that does not consist of only one type of particles. Particles here may mean molecules or atoms. Simple molecular compounds are said to be pure when it consists of molecules which are made of particular elements combining in a certain ratio. Any molecule which are not made of the same elements or are combined in a different ratio will make the compound impure. For elements too this definition applies.
For Giant molecular covalent structure, there is a particular pattern of combining- for example diamonds are made of tetrahedrally bonded carbon atoms. Graphite consist of hexagonal rings of carbon atoms. If we find sulphur in a sample of graphite instead of carbon we can not call that a sample pure.
FOr ionic structure, there is a pattern of combination in hte crystals such as in sodium chloride, each sodium ion is surronded by the same number of chlorine ions as the number of sodium ions surrounding each chlorine ion. THere can not be any impurity within an ionic structure but if a sample of sodium chloride is mixed with sand or some other compound, we will call that sample impure.
The basic definition that we find in high school chemistry is, however, the one I mentioned in the first para.

Answer 2

Main Entry: im·pu·ri·ty
Pronunciation: (")im-'pyur-&-tE
Function: noun
Inflected Form(s): plural -ties
1 : something that is impure or makes something else impure
2 : the quality or state of being impure

Answer 3

1. The quality or condition of being impure, especially:
a. Contamination or pollution.
b. Lack of consistency or homogeneity; adulteration.
c. A state of immorality; sin.
2. Something that renders something else impure; an inferior component or additive.

http://www.thefreedictionary.com/impurity