Racemic modification and epimerisation

What is racemic modification ?

It has been observed that an equimolecular mixture of a pair of enantiomers is optically inactive.This is to expected,since enantiomers have equal but opposite rotatory power. Such type of a mixture is said to be optically inactive by external compensation and is known as a racemic modification. 
It is denoted by (+,ー) . For example, ( +,ー)lactic acid.

What is resolution ?

The process of separating a racemic modification into its enantiomers is known as resolution.

What is epimers ? 

Aldoses which produce same osazones must have identical configurations on all their asymmetric carbon atoms except the alpha (α), such sugars are known as epimers.
For example, glucose and fructose forms same osazone with 3 moles of phenyl hydrazine.Hence they are epimers to each other.

What is epimerisation ? 

The change of configurations of one asymmetric carbon atom in a compound , containing two or more asymmetric carbon atom is known as epimerisation.
For example , glucose epimerise into mannose are as follows.

Summary.
What is racemic modification ?
What is resolution ?
What is epimers and epumerisation? 

Click here: Enantiomers,diastereomers and homotopic.