Elderly applies to the stage of life that begins at the end of middle age. When used as a noun in referring to older persons in general, it is relatively neutral, denoting a group of people whose common characteristic is advanced age: policy issues of special interest to the elderly. However, when used as an adjective in describing a particular person, elderly has a range of connotation that goes beyond the denotation of chronological age to include the various effects of aging. On the one hand, it can suggest dignity; on the other, frailty or diminished capacity. While there is no reason to avoid elderly as an adjective, you should keep in mind that a phrase such as the elderly couple in the second row is likely to conjure a more specific—and probably older—image than if the couple were described as older.
