A ready response to any kind of conversation.
OK or Okay is quintessentially an American English word, one of the few, that has spread to other languages.
The story of origin of OK is quite interesting.
Okay is convenient, easy to use, short and suits almost anywhere and everywhere in the conversation, except as response to a question!
I remember reading "Horn O.K. Please" at the back of Indian trucks, but why O.K. written in between still perplexed me. Finally I found a satisfying answer:
"My logic to this 'Horn OK Please' is: Truck is informing the vehicle behind, 'Horn Please', if it has to overtake. In reply, the vehicle behind agrees and says,'OK'. That's why the fonts are different for these 2 terms." - K G Pawan Kumar, Mumbai.
It fits in everywhere !!
Okay, or OK has been shrunk to 'k' in online chats and SMSs. It can't get any shorter!
P.S. - Any other word with universal/widespread utility? Fuck.
To avoid using the F word, a person might forcefully use the O word, OK! :D