Boyd’s Bible Dictionary:
Among Jews the first-born son enjoyed the right of consecration (Ex. 22:29); great dignity (Gen. 49:3); a double portion of the paternal estate (Deut. 21:17); right to royal succession (2 Chron. 21:3).
Concise Bible Dictionary:
Jacob when dying said of Reuben “Thou art my firstborn, my might, and the beginning of my strength, the excellency of dignity, and the excellency of power.” This is what he was as the firstborn, for in himself he was “unstable as water” and he should not excel (Gen. 49:3-4). He forfeited his birth-right for defiling his father’s bed, and it was given to Joseph, who in Ephraim and Manasseh had a double portion among the tribes (1 Chron. 5:1). The law declared that if a man’s first-born son was by a wife he hated, he must not put the son of another wife in his place: the first-born must have a double portion of all that the man possessed “for he is the beginning of his strength: the right of the first-born is his” (Deut. 21:16-17). Esau is called a profane person for selling his birth-right: it was a privilege God had given him, and which he should have valued as such (Gen. 25:31-34; Heb. 12:16).
Strong’s Dictionary of Greek Words:
Transliteration:
prototokia
Phonic:
pro-tot-ok’-ee-ah
Meaning:
from 4416; primogeniture (as a privilege)