ˈeldə̇st adjective
Etymology: Middle English, from Old English yldest, ieldest, eldest, superl. of eald, ald old — more at old
: of the greatest age or seniority:
a. archaic : most ancient : earliest
let us pay heed to our eldest scientific brothers and shrewdest symbolists, the mathematicians — Weston La Barre
b. : firstborn , oldest
when their eldest child was arriving at school age — F.L.Allen