English grammar rule A uncountable

You can only use the indefinite article with singular, countable nouns. Definite articles must be used with uncountable nouns, but always in the singular form (this, that). Also, don’t use a or an with any other determiner. .

Examples of 'A uncountable' rule

Incorrect	You have already received a that book.
Correct	You have already received that book.
Incorrect	Jennifer spent time in a traffic this morning.
Correct	Jennifer spent time in traffic this morning.