Lo is one of those words that doesn't always have a clear definition — and it can function in at least three different ways, as a subject pronoun, object pronoun or definite article. When you run across the word in a sentence and don't know what it means, you often need to figure out first how it is being used.
Here, in rough order of how common they are, are the ways that lo can be used:
As a masculine direct-object pronoun: In such cases, lo can be translated as either "him" or "it." The feminine equivalent is la.
- ¿Pablo? No lo vi. Pablo? I didn't see him.
- El coche es muy caro. Quiero comprarlo. The car is very expensive. I want to buy it.
- Dámelo. Give it to me.
- No creo que lo hayas conocido. I don't think you've met him.
Note that in the above sentences where lo means "him," referring to a person, it would be very common in some areas, particularly in Spain, to use le instead of lo. The use of le as a direct object pronoun is known as leísmo.
As a neuter definite article: The definite articles in Spanish, typically el and la when singular, are the equivalent of the English "the." Lo can be used as a neuter definite article before an adjective to make an abstract noun. For example, lo importante can be translated as "the important thing," "that which is important" or "what is important."
- Lo bueno es que hemos sido más listos. The good thing is that we have been more clever.
- Lo barato sale caro. What seems cheap ends up expensive.
- Lo mejor es que me voy a casa. The best thing is that I'm going home.
- Lo mío es tuyo. What is mine is yours.
- El entrenador se especializa en lo imposible. The coach specializes in the impossible.
As a neuter direct-object pronoun: Lo can be used as an object pronoun to refer to something abstract, to an unnamed activity or situation, or to a previous statement:
- No podemos hacerlo. We can't do it.
- No lo comprendo. I don't understand it.
- Mi religión no lo prohibe, pero cada vez que lo hago, le doy las gracias al animal por darme vida. My religion doesn't prohibit it, but every time I do it, I give thanks to the animal for giving me life.
With ser and estar to refer to a preceding noun or adjective: This is especially common when answering questions:
- —¿Es nueva tu computadora?. —No lo es. "Is your computer new?" "It isn't."
- —¿Estaban felices?. —Sí, lo están. "Were they happy?" "Yes, they were."
As part of lo que or lo cual: These phrases serve as relative pronouns usually meaning "that," "what" or "that which":
- (Título) La marihuana: Lo que los padres deben saber. (Headline) Marijuana: What parents ought to know.
- Mis padres me daba todo lo que yo necesitaba. My parents gave me everything that I needed.
- No puedo decidir lo que es mejor. I can't decide what is better.
- No todo lo que brilla es oro. Not everything that shines is gold.
As part of lo de: The phrase can be translated differently depending on the context, but generally means something like "the matter concerning":
- Los senadores republicanos fueron informados sobre lo de la CIA. The Republican senators were informed about the CIA matter.
- Lo de que las niñas japonesas se perdieron no era una mentira. The story about the Japanese girls getting lost wasn't a lie.
- Lo de Castro es todo pretextos y mentiras. Castro's way of doing things is all pretexts and lies.
In various phrases: Some examples:
- a lo largo de, throughout
- a lo lejos, in the distance
- a lo loco, like crazy
- a lo mejor, probably
- lo sabe todo, he/she knows it all
- por lo general, generally
- por lo menos, at least
- por lo pronto, for now
- por lo tanto, as a result
- por lo visto, apparently
Loísmo: In some regions, you may occasionally hear the use of lo as an indirect object instead of le. However, this practice, known as loísmo, is considered substandard and should be avoided by those learning the language.