The Spanish definite articles

In Spanish there are four definite articles: el, los, la, las plus the neutral article lo. This might create some difficulties for English speakers since in English there is only one "THE". It's important for spanish learners to remember that in Spanish articles need to agree in number (singular-plural) and gender (femenine-masculine) with the  nouns they preceed. For example:

El libro (masculine-singular)
La mesa (femenine-singular)
Los lapices (masculine-plural)
Las casas (femenine-plural)

Some words will take a neutral article. This is the case when the noun is abstract. For example:

Lo imaginario
Lo impresionante