A word that comes from the Greek translation of the Hebrew word for “firstborn.” It is not found in the Bible. It is a concept that reflects the special status and inheritance rights granted to the firstborn male child.
If the firstborn died, the next oldest living male did not receive the rights of the firstborn. A firstborn female also did not receive these rights, and neither did the firstborn if he was born of a concubine or of a slave woman (for instance, Genesis 21:10).
The Scriptures put a lot of importance on the rights of the firstborn as seen in the distinction between the firstborn and other sons (Genesis 10:15; 25:13; 36:15), the double portion to be given to the firstborn (Deuteronomy 21:17), as well as the special blessing their fathers gave to them (Genesis 21:1–14; 27:1–29; 48:18).