You may know that Americans say “a hypothesis” but Brits say “an hypothesis”. And, as far as I know, both forms of the article are correct.
But why does nobody say, “I gave her an hyacinth”, when referring to the flower? After all, both words begin with the “hi” sound with a long “i”. And both begin with the spelling “hy”. It’s always, I gave her a hyacinth.”
Likewise, no OB GYN says, “Here is an hymen,” when referring to the female tissue. Yet it’s the same “hi” sound with a long “i.” I’m sure there are similar words that are preceded with the article “a”.
I’m also sure there are rule for why things are like this, and certain that some readers will know those rules, but I can’t imagine how they make sense.
One thing’s for sure: I’ll never be able to bring myself to say “an hypothesis.”