A student of Spanish learns very early that the articles vary according to the gender and number of the following noun. Articles are those little words that accompany nouns: “the” or “a” in English–telling you whether the noun is referring to a specific thing (definite) or a non-specific thing (indefinite). Since nouns in Spanish belong to one of two gender classes and nouns may be singular or plural, there are many more forms of the article, as in this chart:
There is a third neuter article, lo.
This article has no plural. It has a wide range of use before adjectives and certain other parts of speech to make them into nouns:
true - That Which is true as possible - That Which is possible mine - mine, That Which is mine
(Compare this with la mía, which would refer to an antecedent feminine noun.)
lo difícil — the difficult thing lo importante — the important thing
Notice that lo is used where the referent idea is not some specific thing but rather an abstract situation or collection of unidentified things:
It happened to me the same. - The same thing Happened to me. What the boss already solved. - The problem Regarding the boss is Already solved.
This same neuter gender also shows up in the neuter demonstrative pronouns, esto, eso and aquello, more or less corresponding to “this, that and the other.”
Hand me that. - Hand that me (thing). What is this? - What's this? I do not want to argue that the other day. - I do not want to argue the issue of acerca the other day.
These neuter demonstrative pronouns, like lo, the neuter article, also never occur in the plural and never refer to a gendered word but rather to unidentified or abstract situations or things.
In you will see how useful neuter can be in conversations.