Use of tú

Question

If I am 70 and my neighbour is 50, why can´t I use tú instead of usted?

Answer

Hello Kay,I think this is all about familiarity. The use of "usted" is for addressing someone you don't know very well, in formal situations or who is elderly. If you know your neighbour fairly well or at least speak to them regularly beyond the courteous "good morning", I would think the use of "tú" would be acceptable. In the same way, they could speak to you using "tú." I speak as an older person and have found that people use "tú' a lot towards me.... and expect it!! In some parts of Spain "usted" seems to be used quite rarely. Perhaps that has influenced my view - the teachers will clarify it.SaludosJohn

Answer

I am not far short of 80 - and regard it as a compliment when young people (in their twenties) address me as "tú". [This^ sometimes happens - but not always; shop assistants usually tend to use "usted"].

My Spanish teacher [in southeast Spain] says she has never in her life addressed a person directly as "usted" - not even when meeting them for the very first time. [It is difficult, though, to imagine her having done that with the teachers/headmistress in her Primary School. I did ask her what she would do if she met the King or the President, and she admitted that she might have to concentrate and discipline herself if that ever happened - or she might just forget ! ... through not being accustomed to "usted"].

Because of the ambiguity of usted with the third-person he/she, I tend to use "tú" almost always, even on a first encounter. To begin with, I addressed our Alcalde as "usted", but not any more; [he doesn't seem to mind].

Answer

Hola Kay,
It is exactly as John and David are saying. There is no strict rule about the use of tú and usted. At the end of the day it depends on the type of relationship and familiarity you have with someone; if you have a very close relationship with your 75 year old neighbour, i.e. you stop to chat every time you bump into each other and ask each other favours, then the fact that she is 75 won't make you use usted, you both may be more confortable using tú. It is though a lot more common to stick to the usted form if you go to a shop or a bank for example. This is simply protocol. The different situations explained in the lesson for the use of one pronoun or the other are those that we consider the most common ones. The good thing is that  it is unlikely to offend someone just because they are not called "usted"; as long as the speaker speaks politely and using a nice tone, using tú is generally OK. 
Saludos
Inma

Answer

Sometimes people at counters address me using “joven”, which is a complement.