Well, I would nearly omit my problem of capital if it were not for your reminding, thank you : )

"OK" is actually the correct word academically, but more often "ok", "Ok", "okay", and "Okay" are used, especially since you're not suppose to use it in academic writing anyways.

Thank you, Timothy. You have perfectly answered my question, thank you very much : )

I'm not sure what you are asking? I'll try to correct what I can see here. Is this sentence okay? (using OK is fine I guess) Is this sentence grammatically correct? What do you call this? What do you refer to this as?