vs
QUICK ANSWER
"Si" is a form of "si", a conjunction which is often translated as "if". "Lo vi" is a phrase which is often translated as "I saw him". Learn more about the difference between "si" and "lo vi" below.
si(
see
)A conjunction is a word that connects words, phrases, clauses, or sentences (e.g., The cat and the dog slept.).
A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
lo vi(
loh
bee
)A phrase is a group of words commonly used together (e.g., once upon a time).
a. I saw him
Ayer llegó mi hermano. - ¡Sí! Lo vi en la biblioteca.My brother arrived yesterday. - I know! I saw him in the library.
b. I saw it
¿Sabes por casualidad dónde está mi teléfono? - Lo vi sobre la mesa.Do you happen to know where my phone is? - I saw it on the table.
c. I saw you
Anoche lo vi caminando por la calle, pero usted no me vio.I saw you walking along the street last night, but you didn't notice me.
