Writers often mix up these words, which leaves me scratching my head why.

Hypothesis is singular, as in The study’s results proved the first hypothesis to be true.

Hypotheses is plural, as in Researchers weighed competing hypotheses to determine which one merited testing.

A side note: In science, a hypothesis is a proposed explanation. It is tested and then the test(s) are duplicated by other scientists. Once several hypotheses supporting a theory are proven to be true, then the theory is thought to be true, at least in principle, as well.

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My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.