OK meaning
EN
[oʊkeɪ] WOK
- "OK" (also spelled "okay", "ok", or "O.K.") is a word denoting approval, acceptance, agreement, assent, or acknowledgment. "OK", as an adjective, can also express acknowledgment without approval.
- As an adjective, "OK" means "adequate", "acceptable" ("this is OK to send out"), "mediocre" often in contrast to "good" ("the food was OK"); it also functions as an adverb in this sense.
EN ok 
- NounPLOKs
- endorsement; approval.
- We can start as soon as we get the OK.
- endorsement; approval.
- VerbSGOKsPROKingPT, PPOKed
- AdjectiveCOMmore OKSUPmost OK
- all right, permitted.
- Do you think it's OK to stay here for the night?
- satisfactory, reasonably good; not exceptional.
- The soup was OK, but the dessert was excellent.
- in good health or a good emotional state.
- He's not feeling well now, but he should be OK after some rest.
- all right, permitted.
- AdverbCOMmore OKSUPmost OK
- satisfactorily, sufficiently well.
- The team did OK in the playoffs.
- satisfactorily, sufficiently well.
- Interjection
- Used to indicate acknowledgement or acceptance.
- I promise to give it back. Reply: OK.
- Let's meet again this afternoon. Reply: OK.
- Shut up! Reply: OK, OK.
- An utterance expressing exasperation, similar to "all right!".
- OK! I get it! Stop nagging me!
- Used to introduce a sentence in order to draw attention to the importance of what is being said.
- OK, I'm thinking of a number...
- Used to indicate acknowledgement or acceptance.
- Proper noun
- Acronym of Oklahoma, a state of the United States of America.
- Acronym of Oklahoma, a state of the United States of America.
- More Examples
- Used in the Middle of Sentence
- I'll cross my fingers that everything turns out OK for you.
- Listen, the only reason I yelled at you was because I was upset, OK ? Good children listen to their parents.
- Used in the Middle of Sentence
Definition of OK in English Dictionary
- Part-of-Speech Hierarchy
- Adjectives
- Adverbs
- Interjections
- Nouns
- Countable nouns
- Proper nouns
- Countable nouns
- Verbs
- Adjectives
Source: Wiktionary
Grammatically, this word "OK" is an adjective. It's also an adverb. It's also an interjection. It's also a noun, more specifically, a countable noun and a proper noun. It's also a verb.