The phrase "a key defining" is not correct as it is incomplete and lacks context.
It could be used in a context where you are describing something that is crucial in defining a particular concept or characteristic.
Example: "The study revealed a key defining feature of the species that sets it apart from others."
Alternatives: "a crucial defining" or "an essential defining".
Consider, for example, the proposal that parental worklessness be a key defining feature of the new child poverty measure.
The analyses include the effect of third-order dispersion, which is a key defining parameter of this type of transmission systems.
But François Hollande has become so weak – even more so with this week's resignation of his economics minister, Emmanuel Macron – and terrorism has transformed French politics to such a degree that Le Pen's prospects now stand out as a key defining factor of where France, and Europe for that matter, may be heading.
On the other hand, a key defining characteristic of an ecosystem is that it emerges, often in unpredictable ways.
That intimacy, that connection to women's self-perception is a key defining characteristic of why women like beauty products.
A key defining characteristic of a persona is that it presents a largely consistent view of an individual.
This is especially likely if you have been told how intelligent you are during your formative years, creating a self-awareness that intelligence is a key definer of who you are.
Understanding the molecular mechanism that regulates breast cancer metastasis is critical to developing therapies to treat breast cancer and increase the survival rate; and defining markers that predict metastatic potential will be a key for defining therapeutic approaches.
A key-defining feature is calcification, but this can have a variable appearance [ 4].
Despite its flaws and regional variations, public health care is generally a key to defining Canada.
Before the Israeli attack, a key question defining outside attitudes about the more than two-year-old conflict was whether chemical weapons had been used, which could draw Western powers more directly into the war.
