“4th” (fourth) means:

• The ordinal form of 4, showing position in a sequence.
  • Example: She finished 4th in the race = she came in position number four.
• It can also refer to:
  • The 4th day of a month (e.g., July 4th)
  • The fourth item, rank, or place in an ordered list

In short, it means number four in order or rank.