Common time is represented by 4/4 and is one of the most commonly used time signature found in music. Just like any other time signature, the top number determines the amount of notes in a measure and the bottom number determines the type or length of note in each. So, 4/4 simply means that there are four quarter notes in one measure. However, this is not always the case. Eighth notes, whole notes and even dotted notes can appear or used in 4/4 time. As long as the measure consists of a constant beat equal to four quarter notes, the rhythm is constant and unaltered.