Using Uncountable Nouns As Countable Nouns

The dictionary says this word is both countable (at least singular) and uncountable; where should I use it as a countable with an indefinite pronoun (a/an), and where should I use it as an uncountable noun (with no article, just the noun)?

This is a question that many article-usage-obsessed ESL learners ask when they see an English word that the dictionaries mark as both uncountable and countable. This idea applies to 90 percent of uncountable nouns.

This is a 90%-accurate answer to the question.

Such nouns are uncountable when they mean the total PROCESS, and they are countable (at least singular) when they mean a single INCIDENT, INSTANCE, or ACT of that process.

For example,
RAPE is a noun that is marked as both.
1. He was convicted of rape. 
Here, rape is an uncountable noun because it is intended as a term or process.
2. What happened to her was a mind-numbing rape.
Here, rape is countable because we are referring to one instance of rape.

3. We get less rain year-round.
Here, rain is singular because it is used rather as a term.
5. We had a heavy rain yesterday.
Here, rain is counted because it refers to one specific rain with the use of an adjective.

5. Love is a feeling that puts the mind at ease.
Here, love is uncountable because it is used as a term.
6. I have a strong love for literary men.
Here, the speaker intends to express a specific love for something.

 

As a bonus, in sentences where usually uncountable nouns are counted, we can see a phrase or noun that introduces one specific case as the subject of the sentence or the prepositional phrase of the noun.

Please be reminded that there are still those uncountable nouns that do no follow this concept.