Partitive + Uncountable noun
Incorrect : He bought a soap.
Correct : He bought a bar/cake of soap.
Incorrect : She gave me an advice.
Correct : She gave me a piece of advice.
Note: You cannot use a, an or one before an uncountable noun. Instead, you should use a partitive (a phrase like "a piece of", which is used before an uncountable noun to express quantity) before it.
