key to

key to (something)

1. noun The most important determining factor needed to achieve or accomplish something. The key to writing fiction is to make something that you would want to read. Anything else will just feel insincere. Everyone wants to know the entrepreneur's keys to success.
2. noun That which provides a clearer or more robust understanding of something. This clue could be the key to the criminal's identity. Nuclear scientists are still searching for the key to cold fusion.
3. adjective Having primary importance to ensure the success of something. Strong leadership is key to any successful business. You are key to our plans, Mary. Please, let me know what we can do to convince you to stay with the company.
4. verb To make sure that something matches or is consistent with something else. A noun or pronoun can be used between "key" and "to." If you don't key your expectations to your students' actual abilities, you'll just end up disappointed.
See also: key
Farlex Dictionary of Idioms.

key to

v.
To make something correspond to something else: I wrote up a teaching guide and keyed it to the materials for each lesson. The worksheets were keyed to the requirements for each course.
See also: key
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • add in
  • a straw will show which way the wind blows
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?
  • all for the best
  • a thing of the past
  • a slew of (something)
References in classic literature
On the table before him they set food and water and upon the opposite end of the table they laid the key to the fetter.
The key that lay there on the table before him was the key to that very lock.
While it was thus engaged Ghek took his spider-like way along the table to the opposite end where lay the key to the fetter.
"How should I, a prisoner, know better than my jailer the whereabouts of the key to my fetters?" he retorted.
The Chessmen of Mars
It cost Boxtel two days more to bring his key to perfection, with the aid of a small file.
The Black Tulip
He had managed to coax old Brus, the gardener, into letting him have the key to the little postern gate on the plea that he wished to indulge in a midnight escapade, hinting broadly of a fair lady who was to be the partner of his adventure, and, what was more to the point with Brus, at the same time slipping a couple of golden zecchins into the gardener's palm.
Whatever else of mischief De Vac might be up to, Brus was quite sure that in so far as the King was concerned, the key to the postern gate was as safe in De Vac's hands as though Henry himself had it.
That night De Vac took the key to a locksmith on the far side of London; one who could not possibly know him or recognize the key as belonging to the palace.
The next day he returned the original key to Brus, telling the old man that he had not used it after all, since mature reflection had convinced him of the folly of his contemplated adventure, especially in one whose youth was past, and in whose joints the night damp of the Thames might find lodgement for rheumatism.
The Outlaw of Torn
The key proffered him by the bereaved widower being a large one, he slips his two-foot rule into a side-pocket of his flannel trousers made for it, and deliberately opens his flannel coat, and opens the mouth of a large breast-pocket within it before taking the key to place it in that repository.
The Mystery of Edwin Drood
All she thought about the key was that if it was the key to the closed garden, and she could find out where the door was, she could perhaps open it and see what was inside the walls, and what had happened to the old rose-trees.
Secret Garden
But nowhere in the whole boat could they find a key to fit that lock.
Story of Doctor Dolittle
The chambermaid returned, completed her work, locked the door of the dressing-room on the inner side, locked the principal entrance-door on leaving the room, and returned the key to Agnes in the drawing-room.
The Haunted Hotel
From the perspective of the foreign key, once you have assigned a foreign key to a row, either at insertion or afterward, you must decide whether that value can be changed.
The importance of referential constraints
That scheme allowed a different permanent key to be created for each user and considerably reduced the computation of keying material.
ZIMMERMANN REAL-TIME TRANSPORT PROTOCOL FOR HIERARCHICAL KEYS GENERATION OF ENCRYPTED SCALABLE VIDEO STREAMING