What is a hetroatom And What is the hetroatom in alcohol functional group

What is a hetroatom And What is the hetroatom in alcohol functional group? 

Answer: In a hydrocarbon chain, one or more hydrogen atoms can be replaced by other atoms according to their valencies. 

The element which replaces hydrogen in the chain is called a

heteroatom. e.g. in  alcohol (-OH) functional group.Oxygen is A Hetroatom