That's epsilon, not ypsilon (it just occurred to me that it's more common to see it called "upsilon" in English, though I don't know why based on how the letter is pronounced - "eee-psilon")
That's epsilon, not ypsilon (it just occurred to me that it's more common to see it called "upsilon" in English, though I don't know why based on how the letter is pronounced - "eee-psilon")