"entendieron ustedes lo que dije," why used in second person?
 

entendieron ustedes lo que dije. From what I understand, this sentence translates into something like, "You understood what I said?" What I'm having trouble with is, why is entender conjugated in third person plural form? If you're talking in second person wouldn't it be "Entendio usted lo que dije" or "Entendiste lo que dije"? And I know it's being used in second person because of the context I'm reading it from. Thanks for any help.

'They' or 'you (plural)' is an acceptable English subject pronoun for that conjugation, but not 'you (singular, formal)' or 'you (singular, familiar)'.

The Spanish second person has the following singular pronouns: tú and usted (vos is used in some countries instead of tú)
It has the following plural pronouns: vosotros,-as and ustedes

The conjugation entendieron is both a second- and a third-person plural construct. It is a second-person construct when the subject pronoun is ustedes. It's a third-person construct when the subject pronoun is ellos or ellas.

In Spain, the second-person plural familiar form is vosostros,-as entendisteis, but in Latin America, the second-person plural familiar form is ustedes entendieron.

Adding to Rusty's right explanation: You already know "entendió usted", which also uses a third person conjugation; "ustedes entendieron" is the same, just in the plural form.
In Spain, "vosotros" is used for a group of people to whom you speak using "tú", and "ustedes" for a group of people you talk to using "usted". In Latin America we use "ustedes" for everyone in the second person plural. :D


- Juan, ¿tú conociste a mi abuelo?
- Juan y Laura, ¿vosotros conocisteis a mi abuelo? (In Spain, although they might prefer present perfect instead of preterite.)
- Juan y Laura, ¿ustedes conocieron a mi abuelo? (Latin America.)

- Profesor López, ¿usted conoció a mi abuelo?
- Doctora Martínez y profesor López, ¿ustedes conocieron a mi abuelo? (Everywhere.)


- Ana, ¿en qué fecha te casaste (tú)?
- Ana y Luis, ¿en qué fecha os casasteis (vosotros)?
- Ana y Luis, ¿en qué fecha se casaron (ustedes)?

- Señor Hernández, ¿en qué fecha se casó (usted)?
- Señor y señora Hernández, ¿en que fecha se casaron (ustedes)?