Or is it just regional spelling, language difference?
Yeah..I’m dumb.
Huh hay?
I have zero idea what you’re asking.
Wikipedia says it’s a different spelling of the same thing.
Cay - Wikipedia
Ah hah! Now I (maybe) get it.
Don’t confuse that with a “quay” which is a man-made wharf properly pronounced pronounced “key”, despite wiki’s silly ideas:
Thanks. Now I know. 
Melanie Safka is rolling in her grave.
Then WTF is a “quay”?!
Second cousin to a quack.
The dessert was originally named, Quay Lime Pie, until the inventors got sick and tired of correcting everyone pronouncing it “Kway.”
ETA: Sorry, wrong thread.
So key and cay are small islands pronounced like “key”. And “quay” is a wharf pronounced like “key”.
So what’s the the key lesson here? For one syllable words it doesn’t matter how it’s spelled. It’s always pronounced “key”.
So when you see “The red duck ate muck near the quay on the cay”, say “Key key key key key key key key key key key” and you’ll be doing it right. 
So, a key and/or a key can have a key, but a key doesn’t necessarily have to be on a key and/or a key, ‘kay?
Que?
Como? 
Yeah, something about like that. Well done!
Yay!
I remember getting into a bit of an argument with a teacher about that word in kindergarten. I for some reason was fascinated by the pronunciation guide in the classroom dictionary. She insisted it had to be pronounced “quay,” and I remember thinking it weird that she didn’t understand the pronunciation guide saying it was pronounced (kē), but had to read the homophone list to find out I was right.
Though, unfortunately, @LSLGuy, even that dictionary had (kwā) as a secondary pronunciation.
I also remember that buoy can sound like boo-ee or boy.
A Boo-ee knife?
That’s not a knife.
You were very precocious to have dictionary abilities in kindergarten.
I liked the dictionary early. With my difficulty speaking I was always looking at key to pronunciation. If I had trouble I bounced down to the homophones.
Your teacher being a kindergarten teacher was teaching to the age level not your personal intelligence. Which I think is kinda the way it is in early grades. She probably never thought you were looking at the key to pronunciation of the word.
The first Bowie knife was made right down the road from me. In Washington, Ark.
I assure it’s a helluva knife.
Now, wait just a consarn minute — how did you get “Yay!” past Discourse?
Yeah, I was a kid. I didn’t realize this just wasn’t just stuff everyone knew. There was a small guide on every page, and a huge guide at the front of the dictionary. (And, to be clear, this was a kid’s dictionary, I’m sure.)
Also I might have been a first grader. I had the same teacher and classroom for both years. Montessori is very “go at your own pace.”
I just couldn’t resist talking about quay. It’s one of my earliest memories.