1. An exclamation of surprise, pain, or anxiety.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• ch,
• och,
• othe,
• ph,
• ohau,
• gh,
• ocuh,
• foh,
• om,
• jh,
• owch,
• wh,
• ohpe,
• ohua,
• og,
• yh,
• moh,
• ot,
• boh,
• ohia

• ohio,
• o.

The plural form of the word "oh" is "ohs"

The singular form of the word "oh" is also "oh". It is an interjection expressing surprise, joy, or other strong emotions. It does not change its form in singular or plural usage.