when do you need an article?

A single, countable noun must have an article if there is no other number, determiner or possessive (e.g. two, our, this). If the noun is plural, an article may not be necessary. Look first at your noun: our house – you do not need an article, because you already have the possesive our. this year – you do not need an article, because you already have the determiner this. car – you need an article, because this is a singular countable noun with no determiner already. trees – you may need an article, depending on whether the noun is definite or not. For example: Trees are usually green – no article is needed, because you are talking generally and the noun is not definite, i.e. you are not talking about specific trees. The trees in the park are green – the article is needed because you have specified which trees you are talking about