What is the meaning of Fourth?

The ordinal form of the number four.

The person or thing in the fourth position.

A quarter, one of four equal parts of a whole.

The fourth gear of an engine.

A musical interval which spans four degrees of the diatonic scale, for example C to F (C D E F).

To agree with a proposition or statement after it has already been thirded.

Alternative form of ferthe

Source: wiktionary.org