Some more words: union, behavior, Daniel.
And the second i in opinion, familiar, brilliant, California.
I am especially concerned with American English.
Contrary to what you learned in school, there are more than just vowels and consonants. In words like 'onion', the i serves as a semi-vowel, or glide. This is represented in IPA as
/ˈʌn jən/ and the letter i represents the
/j/ sound, which is the same sound as at the start of the word "yes".
Vowels and consonants are not letters, but sounds that are represented by letters. The second ‘i’ in ‘opinion’ represents the sound /j/, which I have seen described as both a palatal glide consonant, and a palatal semi-vowel.
Have a look at a Webster dictionary, if in the American way of sound-script you find the sign y you may consider the sound of the letter i as a consonant, no matter how complicated the description of this sound by phoneticians is.
Yes, probably, because Hebrew uses the character Y as a consonant for this phoneme, so onion, view and Daniel may be/are Hebrew, and California would count as well. The term 'glide' has emerged most likely in the absence of an understanding of the Hebrew source. In fact English has, at the last count, 11 different morphologies for this 'yoo' sound, i.e. cue, you, stew, queue, etc., all of which would seem to be variants on the Hebrew. If it's a 'Y', or a glide, in the phonetics, it's probably Hebrew. If the glide is vacant, for example wing, mint, ride, then it won't be a Hebrew Y (or yud) but Hebrew also has an 'i' (in Masoretic Hebrew). Either way, it's probably Hebrew and although I can't give you chapter and verse on this, the sources which are usually given for English in the dictionary would seem themselves to be Hebrew derivations, so there really isn't much choice, but you have to know Hebrew and I have yet to meet an English language linguist who does. Hebrew speakers will understand what I am saying more easily, I suspect. Hope this helps. Amen.