Sorry, I have a query regarding these two sentences.

First sentence:

An elderly care service association is urging the government to allow temporary entry of foreign workers trained in nursing and caregiving to address the shortage of such staff at elderly care homes nationwide.

Second sentence (Written by myself):

A segment of the population may be facing a shortage of food in the future.

Question:

For the second sentence, can I substitute 'a shortage of food' for 'the shortage of food'? At first, I thought the word 'shortage' is often written in the company of 'a' until I came across the first sentence. But I cannot find a sentence with 'the shortage of food' in it on the internet. Is "the shortage of food" exist?

In English, "a" is called the indefinite article, whereas "the" is called the definite article. We use "the" when referring to a particular/previously mentioned/assumed to be known thing. Otherwise, (if an article is required) we use "a".

teal desk 749For the second sentence, can I substitute 'the shortage of food' for 'a shortage of food'?

Note how to use "substitute".

The answer is no. This is because we are not talking about a particular/previously mentioned food shortage.

teal desk 749At first, I thought the word 'shortage' is often written in the company of 'a' until I came across the first sentence.

No. That is not correct. "Shortage" can easily take the definite article.

In the first sentence, we are talking about a particular food shortage - the one at elderly care homes nationwide. The best way to determine whether you need the, is to ask yourself [ which + noun?]. If you can answer that question, then use "the".

teal desk 749But I cannot find a sentence with 'the shortage of food' in it on the internet. Is Does "the shortage of food" exist?

It most certainly is possible.

Click on the following link to see some examples (replace the dots with www)

......fraze.it/n_search.jsp?q=%22the+shortage+of+food%22&l=0

Thank you so much.