The English definite and indefinite articles (the, a, an) don’t have exact parallels in Vietnamese language. Instead of articles, Vietnamese language uses a type of word called classifier to make similar distinctions in nouns.
Cái nhà (lit. classifier + house) = the house
một cái nhà (lit. one + classifier + house) = a house
nhà này (lit. house + this) = this house
This is one of the reasons why using articles in English is so difficult for Vietnamese learners. But, that is not all. Here is the second reason.
Not all Vietnamese words occur with classifiers. More than that, sometimes the absence or presence of a classifier distinguishes between two different but homophonous nouns.
Đường (noun) = sugar
Con Đường (classifier + noun) = the street/road
Vietnamese learners do know that English sometimes uses a definite article, sometimes an indefinite article, and sometimes it doesn’t use any article. However, mistakes still persist and are very difficult to fix because the English system is too different from the Vietnamese one. Hints such as checking whether a noun is countable or uncountable are a real help.
Typical errors I have seen during my time teaching ESL/EFL in Vietnam are:
I would like to be adult, not child.
I am tired so I am going to the bed.
I hope you will hear a good news.
I like to eat in restaurant.