Examples from the Web for first-order
A lot of ink will continue to be spilled about the first-order problems surrounding that fact.
A second-order effect on direction may therefore be produced by irrotational motion, but not a first-order effect.The Ether of Space|Oliver Lodge
In the case of a first-order fixed light the cost of conversion to an occulting characteristic does not exceed 250 to 300.
A first-order issue is how can we augment or improve the use of existing military capability should it be required.Shock and Awe|Harlan K. Ullman