Senior citizen is a common euphemism for an old person used in American English, and sometimes in British English. It implies that the person being referred to is retired. This in turn usually implies that the person is over the retirement age, which varies according to country. Synonyms include old age pensioner or pensioner in British English, and retiree and senior in American English. Some dictionaries describe widespread use of “senior citizen” for people over the age of 65.
When defined in an official context, senior citizen is often used for legal or policy-related reasons in determining who is eligible for certain benefits available to the age group.
The term was apparently coined in 1938 during a political campaign. Famed caricaturist Al Hirschfeld claimed on several occasion that his father Isaac Hirschfeld invented the term “senior citizen.” It has come into widespread use in recent decades in legislation, commerce and common speech.
In commerce, some businesses offer customers of a certain age a “senior discount.” The age at which these discounts are available varies between 55, 60, 62 or 65 and other criteria may also apply. Sometimes a special “senior discount card” or other proof of age needs to be obtained and produced to show entitlement.
The age which qualifies for senior citizen status varies widely. In governmental contexts it is usually associated with an age at which pensions or medical benefits for the elderly become available. In commercial contexts, where it may serve as a marketing device to attract customers, the age is often significantly lower.
In the United States, the standard retirement age is currently 66 (gradually increasing to 67). —Wikipedia