I understand the quotation from poem "If" by Rudyard Kipling, but I don't understand the meaning of the word "turn" in its context
If you can force your heart and nerve and sinew to serve your turn long after they are gone
Serve one's/its turn is an idiomatic expression that means:
Be useful or helpful:
- now that they have served their turn, cut some of them out suppressing his ire would hardly serve his turn at this juncture
(ODO)
- it's a passage about how a person's willpower can win over the weaknesses of the flesh.
