The phrase "a principal difference between" is correct and usable in written English.
It can be used when discussing or comparing two or more items, concepts, or ideas to highlight a significant distinction.
Example: "A principal difference between the two theories is their approach to understanding human behavior."
Alternatives: "a key difference between" or "a major distinction between".
A principal difference between the effects of plasma on materials with the pores of different sizes is demonstrated.
"There is no need to be concerned with sales or other commercial matters," she added, underscoring a principal difference between corporate-sponsored galleries and those that are independent.
A principal difference between over-the-board chess and all forms of correspondence chess is that in the latter players are permitted to analyze a position by moving the pieces and by consulting reference books.
A principal difference between the current and former umbrella units, Interpublic executives said, is that under Mediabrands the media agencies would retain autonomy and remain aligned with advertising and marketing agencies like the McCann Worldgroup (Universal McCann) and Draft FCB (Initiative).
The campaign for Brokerage America carries the theme "Cut to the trade," meant to emphasize what Mr. Sykoff described as a principal "difference between us and our competitors," which is that Garrett, as a market maker in 1,100 Nasdaq stocks, will use its own operations to execute orders, in addition to offering free trades as many other online brokerage firms have done or still do.
A principal difference between oxide and hydride fuels is the high thermal conductivity of the latter.
The diagrams in Figure 12 illustrate in a simplified manner the principal difference between the two contraction mechanisms, that at a cleavage furrow and that at a phagocytic cup.
But the pre-primary debates over the weekend made it clear that the slogan is a reminder of the principal difference between Mr. Huntsman and the front-runner, Mitt Romney: Mr. Huntsman, the Obama administration's former envoy to Beijing, appears to believe what he says.
This is the principal difference between a dog and a man.
Here's the principal difference between the two: Software engineering is typically a group effort, with differing and often fluid roles and responsibilities for the group members.
