I’m having trouble with figuring out formal vs informal and when it’s appropriate to use each. Can someone tell me if you would use tú or usted in the following scenarios?

1) a co-worker you are not friends with

2) a neighbor you see often but don’t talk to much

3) an adult child talking to a parent

4) a customer speaking to a store employee

5) a distant relative you don’t have a close relationship with

6) random person you run into on the street, in a store, at an event, etc.

See a translation

The easiest way you can know is:

It’s an adult or a lot older than you and you don’t know them: USTED

If your working in anything costumer service related then: USTED

If your are talking to teachers, doctors, lawyers, and those kind of professionals then it’s common to called them by: USTED

If they are your grandparents then: USTED / if you are really close to them then TU

If you are friends with that person, any close relationship, close relatives: TU

If they are your same age or younger (even if you don’t know them): TU

Teachers from middle school till university are usually call by TU by their students

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Now despise this a lot of people don’t take formal / informal very strictly.

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1) a co-worker you are not friends with - TU (if it’s your age or younger)
USTED (if it’s a lot older)

2) a neighbor you see often but don’t talk to much - TU (if it’s your age or younger)
USTED (if it’s a lot older)

3) an adult child talking to a parent - if it’s your parent depends on how your parents raise you, you should call them according to how they told you to call them

4) a customer speaking to a store employee - TU but if you want to be polite then TU (if it’s your age or younger)
USTED (if it’s a lot older)

5) a distant relative you don’t have a close relationship with - TU (if it’s your age or younger)
USTED (if it’s a lot older)

6) random person you run into on the street, in a store, at an event, etc. - TU (if it’s your age or younger)
USTED (if it’s a lot older)

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Also a lot of time when they are in a higher position that you, let’s say teachers, parents, grandparents, some professionals, they are going to tell you how they prefer to be call, you can start by speaking to them in a formal way and they will let you know or you can ask “le puedo hablar de tu?”