In comparisons between two persons, elder means “older” but not necessarily “old”:
My elder sister is sixteen; my younger, twelve. Eldest
is used when three or more persons are compared:
He is the eldest of four brothers.
In other contexts elder
does denote relatively advanced age but with the added component of respect for a person's achievement, as in an elder statesman
. If age alone is to be expressed, one should use older
rather than elder:
A survey of older Americans; an elderly waiter.
and its related forms, the adjectives old
, and oldest
are applied to things as well as to persons.
elder 1. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.