make a difference
1. Distinguish or discriminate. This phrase appears in the Bible (Leviticus 11:47): "To make a difference between the unclean and the clean." [Late 1500s]
2. Also, make the difference. Cause a change in effect, change the nature of something, as in His score on this test will make the difference between passing and failing, or These curtains sure make a difference in the lighting.
3. Be important, matter, as in Her volunteer work made a difference in many lives. The antonym of this usage is make no difference, as in It makes no difference to me if we go immediately or in an hour. This usage appeared long ago in slightly different versions. Miles Coverdale's translation of the Bible of 1535 had it is no difference, and the converse, it makes great difference, was first recorded about 1470.