Usted/Ustedes

This is a way of speaking formally to someone, for example an older person or teacher.

For the 2nd person, use the 3rd person ending.

For the 2nd person plural, use the 3rd person plural ending.

E.g.

-To say 'you talk quickly' to one friend: 'hablas rápidamente'.

-To say 'you talk quickly' to one teacher: 'habla rápidamente'.

-To say 'you talk quickly' to two friends: 'habláis rápidamente'.

-To say 'you talk quickly' to two teachers: 'hablan rápidamente'.

'You plural'

Just remember that if you're saying something directed at more than one person, you need to use the 'vosotros', or 2nd person plural form.

See my ‘SOS’ question for further explanations of the persons.