The time signature, represented by the fraction placed at the beginning of the score, tells us what note value lasts a beat and how many beats there are per measure. These fractions have a general meaning, but depending on the musical aesthetics of the time, the writing habits of the composer, the written transcription of music of oral tradition, the phrasing and the tempo, these time signatures can represent very different meters.

Nonetheless, the mathematical meaning of the time signatures is unchanging:  will always be three quarters of the  representing the whole note!