The word lo has several different uses, some of which have no simple equivalent in English. Some uses are presented below, others elsewhere.

Uses presented elsewhere

As a direct object pronoun, the only use in which it shows number or gender or is part of a paradigm (a set of forms).

In relative pronouns lo que, lo cual.

In the comparative phrase lo mismo que...

Other uses of lo are presented below.

Before invariable (masculine singular) adjective
This combination (sometimes call the "neuter article") forms a noun phrase, translating as the (adjective) thing...:

• Lo bueno de no tener que trabajar es que puedo ver las telenovelas.
  • The good thing about not having to work is that I can watch the soaps.
• Lo más impresionante es que ella casi nunca comete errores.
  • The most impressive thing is that she almost never makes mistakes.

Before an adverb or variable adjective
This translates as how (adjective or adverb). Adjectives must agree with the referent noun:

• ¡Mira lo altas que son esas chicas!
  • Look how tall those girls are!
• Esos platos son muy sabrosos para lo baratos que son.
  • Those dishes are very tasty considering how cheap they are.
• Me impresiona lo bien que tu hermana habla inglés.
  • I'm impressed by how well your sister speaks English.

These are pronouns that refer to no particular noun.

Lo de
Translates as the matter of..., the business about...:

• Lo del partido cancelado me enoja.
  • The business about the canceled game makes me angry.
• El profesor no dijo nada sobre lo de los exámenes.
  • The professor didn't say anything about the matter of the exams.

Lo que
A pronoun that variously translates as what, that which, the thing that...; it is not to be confused with the relative pronoun lo que:

• Lo que no entiendo es por qué José no viene.
  • What I don't understand is why José isn't coming.
• Piensa en lo que ha dicho Alicia.
  • Think about what Alicia has said.