Fourth has 8 different meanings across 4 categories:
Noun · Adjective · Adverb · Proper Noun
following the third position; number four in a countable series
"She finished fourth in the race, crossing the finish line just behind her three competitors."
one of four equal parts
"a quarter of a pound"
the musical interval between one note and another four notes away from it
"The violinist struggled to execute the fourth perfectly, as her finger placement was slightly too wide for that specific distance on the string."
The person or thing in the fourth position.
"The student who finished last was fourth because she had been disqualified from the top three spots."
In plain English: The fourth is the number that comes right after three and before five when you count.
"She was fourth in line to receive her prize."
Usage: Use "fourth" as a noun when referring specifically to an individual item or person occupying the fourth place in a sequence, such as "the fourth runner crossed the finish line." It functions identically to ordinal numbers like "first" or "second" when naming positions rather than quantities.
coming next after the third and just before the fifth in position or time or degree or magnitude
"the quaternary period of geologic time extends from the end of the tertiary period to the present"
The ordinal form of the number four.
"She decided to sit in the fourth row because it offered a perfect view of the stage."
In plain English: Fourth means coming after third and before fifth in a sequence.
"She was born in the fourth month of the year."
Usage: Use "fourth" to describe something that comes after three items in a sequence or represents one part of a set divided into four equal pieces. It functions as an adjective before a noun to specify rank, such as the fourth floor, or as part of a fraction like one-fourth.
The Fourth of July.
"We spent the whole day at the beach celebrating the Fourth of July with fireworks and BBQ."
The word fourth comes from Old English fēorþa, which is a combination of the number four and an ordinal suffix meaning "th." It traveled into Middle English as fourthe before settling into its modern form.