I. fourth 1 /fɔːθ $ fɔːrθ/ BrE AmE adjective
[ Language: Old English ; Origin: feortha , from feower 'four' ]
coming after three other things in a series:
in the fourth century
her fourth birthday
—fourthly adverb
II. fourth 2 BrE AmE pronoun
the fourth thing in a series:
the fourth of July
III. fourth 3 BrE AmE noun [countable]
¼; one of four equal parts
one-fourth/three-fourths ⇨ ↑ quarter 1 (1)