Definitions of Ok:

• noun:   an endorsement
• noun:   a state in south central United States
• adjective:   being satisfactory or in satisfactory condition

  Example: "Things are okay"

• adverb:   sentence-initial expression of agreement
• name:  A female given name (rare: 1 in 25000 females; popularity rank in the U.S.: #1547)
• name:  A surname (very rare: popularity rank in the U.S.: #26209)