What age is a person considered a senior?

The most common age to be considered a senior and be eligible for discounts is 55. You might want to consider getting an AARP membership; it only costs about $15 a year and they have lowered the age requirement to 50. Many restaurants will offer discounts if you show the card; if you buy one cup of coffe a day at McDonand's, the discount will pay for the card in a couple of months.