1. (

• fourth

) following the third position; number four in a countable series ;

2. (

• one-fourth ,
• fourth ,
• one-quarter ,
• quarter ,
• fourth_part ,
• twenty-five_percent ,
• quartern

) one of four equal parts; "a quarter of a pound" ;

3. (

• fourth

) the musical interval between one note and another four notes away from it ;

1. (

• fourth ,
• 4th ,
• quaternary

) 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" ;

1. (

• fourthly ,
• fourth

) in the fourth place; "fourthly, you must pay the rent on the first of the month" ;