unsupportable; insupportable.
Both forms are standard and have been since they were first recorded in English in the 16th century.
“Unsupportable” is about twice as common as “insupportable” in American print sources — e.g.: “[A]dding $212 a month for health insurance to food, transportation, and housing costs in this high-cost state might well prove an unsupportable burden.” Editorial, “What’s with This Health Law?” Boston Globe, 29 Dec. 2006, at A14.
But “insupportable” is about six times as common as “unsupportable” in less formal use. And it also appears regularly in edited text — e.g.: “[O]ne can only admire Hood for the effort she makes in this book to describe an insupportable grief.” Julie Wittes Schlack, “Learning to Live After Losing a Child,” Boston Globe, 18 Jan. 2007, at E6.
For information about the Language-Change Index click here.
——————–
Quotation of the Day: “Literature is the last great cottage industry. Every poem or novel is a one-of-a-kind thing, made at home, by hand.” Jay Parini, “On Being Prolific,” in Writers on Writing 199, 199 (Robert Pack & Jay Parini eds., 1991).
