Describing the simplest of many models, languages, relationship, forms of logical discourse etc, or the first in a numerical sequence of such things.(adjective)
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Use "first-order" in a sentence
"However, this first-order effect is not the only way that interreligious marriage can affect interreligious relations."
"Germany's mistake was to consider only first-order effects on bank capital, whereas it would be the second-order contagion effects on government and bank borrowing costs that would do the greatest damage."
"Mr. Obama may be hobbled by a poor economy and unpopular policies, but he is a first-order campaigner."