singular or countable nouns

[masih.ostad]

How can one distinguish between a singular or countable noun since both take an "a" before the word. For example: adjuration in this sentence:

<an adjuration to check the facts carefully before publishing the exposé on corruption in the statehouse>

Thanks

[5jj]

How can one distinguish between a singular or countable noun since both take an "a" before the word.

They don't. uncountable nouns cannot be used with a/an - that's one of their defining features.