The meaning of “בְּכוֹר”

“And Judah took a wife for Er his firstborn, whose name was Tamar.”

“But he shall acknowledge the son of the hated for the firstborn, by giving him a double portion of all that he hath: for he is the beginning of his strength; the right of the firstborn is his.”

“And unto David were sons born in Hebron: and his firstborn was Amnon, of Ahinoam the Jezreelitess;”

“And their father gave them great gifts of silver, and of gold, and of precious things, with fenced cities in Judah: but the kingdom gave he to Jehoram; because he was the firstborn.”

“And the firstborn of the poor shall feed, and the needy shall lie down in safety: and I will kill thy root with famine, and he shall slay thy remnant.”