Articles determine the role of a noun in a sentence, giving it history and context. There are two kinds: the definite ("the") and the indefinite ("a" – or "an" if the noun starts with a vowel sound*).
'A' or 'an' denotes a specified item (one of many):
“China is a country in Asia”
'The' denotes a specified item (unique):
“China is the Asian country with the largest population”
No article means the thing (or things) is unspecified:
“Countries in Asia tend to have fast growth rates”
Sometimes it’s helpful to ask the question “which one(s)?” If the answer is “that one” or “those ones”, then an article is required. If the answer is “all or any of them”, then no article is required:
“Iron ore is used for making steel”Which iron ore? Any iron ore; iron ore in general.
Which steel? All steel.
For this reason, articles are less common for plurals and for things that can’t be numbered:
“Heroin is bad for you” (heroin in general)
“Oranges are good for you” (any oranges)
But you can use articles – even for unnumbered or plural things – if you are specifying something distinct:
“Don’t drink from this river. The water is bad for you”Water might generally be good for you, but this particular water is not. We can apply this to a variation of the earlier example:
“The steel from this plant is made with low-grade iron ore”
Very occasionally, you have a choice.
“Ships on this trade are losing money” orThere is a subtle difference in meaning, but one that is rarely important. You can choose whether to use an article.
“The ships on this trade are losing money”
One other wrinkle is that we don’t use articles for proper names. We never say: the Europe, the India or the Patrick. The only exception is when names are descriptive: we do say: ‘the European Union’, ‘the United States’ and ‘the People’s Republic of China.’ That's why we usually use articles for geographical names: when we say ‘the Ganges’, we mean ‘the Ganges [river]’. Hence we say ‘the Pacific [Ocean]’ and ‘the Himalayas [mountain range]’.
The same rules apply when names are abbreviated:
“NYK” (from ‘Nippon Yusen Kaisha’)
“The US” (from ‘the United States of America’)
That rule only changes when the abbreviation becomes a name itself: when you read it as a word rather than reading each letter separately:
“The Organisation for Economic Co-operation and Development” remains “The OECD”
“The Organization of Petroleum Exporting Countries” becomes “OPEC”, because it's pronounced "Oh-Peck".
There are some other subtleties to this argument, but the above should be enough for anyone struggling with articles in English or most other languages that use them.
* Note I said "vowel sound" rather than "vowel". That's because some words beginning with 'u' start with a consonantal 'y' sound:
"I bought a ukulele (you-keh-lay-lee) from an unhelpful salesman in a Ukrainian (you-kray-nee-an) music shop"Moral: If you give this page a bookmark, you'll be able to find the information again.