Technically, a person is considered a senior citizen when they reach the age of 65. 

However, that's not always the way the general public feels - especially those who have hit the age of 50. 

When AARP (or Saga) starts sending you offers to join their organization, you have essentially crossed over into the 'senior set'.

To some people, this might send them into spasms of denial.  After all, how can you be 60 when you still feel 30 in your mind? 

But, really, that's a good way to think. 

It's been said many, many times that age is simply a number - it's a state of mind how old you actually are!