Different Meaning of Phrase OK

We use the term OK in every field.

I am OK.  By Using the phrase OK it is meant I am well.

‘Okay’ or spelled ‘OK,’ ‘O.K.’  denotes approval, acceptance, agreement, assent, or acknowledgment.

‘Okay’ has frequently turned up as a  yes-word in many other languages.

As an adjective, ‘okay’ means ‘adequate,’ or ‘acceptable. For example, ‘this is okay to send,’ It also conveys ‘mediocre’ often in contrast to ‘good’ for example  ‘the food was okay’. It also functions as an adverb in this sense. As an interjection, it can denote compliance ‘Okay, I will do that’, or it may imply agreement, for example  ‘Okay, that's good’. As a verb and noun it means ‘assent’. For example, ‘The boss okayed the purchase,’ and, ‘The boss gave his okay to the purchase.’ It can also be used with appropriate voice tone—such as sarcasm or a questioning tone—to show doubt or to seek confirmation, assent and approval, for example ‘Okaay?’ or ‘Is that okay?’

There is no consensus on its origin  It is believed that in the First World War the casualty figures were shown daily on a giant board in public as under:

Zero is pronounced as Oh. For example 903=nine oh three. Apply Oh below for Zero.

Date.        Casuality Status.      No.  Killed./injured.

12-12-1914      -                       0          K

13-12-1914.     -                       5          K

Zero is pronounced as Oh.  Therefore No. of Killed on 12^_12_1914 is OK ,=zero killed.

That is how term OK came into usage..