Part of speech: Adjective (satellite)
coming next after the third and just before the fifth in position or time or degree or magnitude
Example: the quaternary period of geologic time extends from the end of the tertiary period to the present
Part of speech: Noun
one of four equal parts
Example: a quarter of a pound
Part of speech: Noun
following the third position
Example: number four in a countable series
Part of speech: Noun
the musical interval between one note and another four notes away from it
Part of speech: Adverb
in the fourth place
Example: fourthly, you must pay the rent on the first of the month
Fourth part, Quarter, One-fourth, Fourth, Twenty-five percent