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? I didn't see him
¿Pablo? No lo (or le) vi.
The car is very expensive. I want to buy it.
El coche es muy caro. Quiero comprarlo.
Give it to me.
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. (May not be good use)
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."
The good thing is that we have been more clever
Lo bueno es que hemos sido más listos.
What seems cheap ends up expensive.
Lo barato sale caro.
The best thing is that I'm going home
Lo mejor es que me voy a casa.
What is mine is yours.
Lo mío es tuyo.
The coach specializes in the impossible.
El entrenador se especializa en lo imposible.
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:
We can't do it.
No podemos hacerlo.
I don't understand it.
No lo comprendo.
As part of lo que or lo cual:
These phrases serve as relative pronouns usually meaning "that," "what" or "that which":
(Headline) Marijuana: What parents ought to know.
(titulo) La marihuana: Lo que los padres deben saber.
My parents gave me everything that I needed.
Mis padres me daba todo lo que yo necesitaba.
The proton is smaller than what is believed.
el protón es más pequeño de lo que se cree.
The results confirm what the same research team already published in Nature in 2010:
Los resultados confirman lo que el mismo equipo ya publicó en Nature en 2010
The proton seems to be 0.00000000000003 millimeters smaller than what researchers thought.
El protón parece ser 0,00000000000003 milímetros menor de lo que pensaban los investigadores.
When lo que refers to an idea or abstract action,
it can almost always be translated as "what" or "that which."
What is happening
lo que pasa
What we have done
lo que hemos hecho
What is worrying me
Lo que me preocupa ??????
Lo que me está preocupando
What we know
Lo que sabemos
What is unforgetable
Lo que es inolvidable