If a story's essential turning point -- what Aristotle called peripeteia -- can be undone at will, the drama starts to leak away.
"This assassination will be an essential turning point for the Kurdish movement all over Syria, where the silent, neutral Kurdish majority will join the revolution and expand their rallies," Jouwan Yussef, a Kurdish activist and friend of Mr. Tammo's, said from Qamishli.
He faced a heartbreaking but essential turning point in his life.
Windows Live Essentials turned out to be less than essential after all.
To call the session scrappy is charitable, though essential landmarks turn up in the right places.
In particular, there are no new policy announcements despite the fact that this will be essential to turn the vision into reality on the ground.
Mr Collins suggests that McKinsey did have the sort of leader that he claims is essential to turn a good company into a great one.
It's essential to turn up the heat full time in Washington for any and every legislative roadblock to administration policy that they and their peers can induce principled or frightened Republicans to endorse.
But it is essential to turn this commission from an Obama-Medvedev inithative that may die once one or both of its principals leaves office into a permanent intergovernmental body that can continue its work as presidents come and go.
The song's trajectory also demonstrates the continuing power of radio, which record executives say is still essential to turn any song — no matter how much online buzz it has — into a genuine smash.
