Whole note (or "breve", hence the British name "semibreve") lasts twice as long as a whole note. A related symbol is the whole rest (or semibreve rest). It usually applies for an "entire measure", but may occasionally mean a rest for the duration of a whole note, in longer time signatures such as or . (An entire measure rest is drawn centered within the measure, whereas a rest lasting for a whole note is aligned to where the note would be.) Whole rests are drawn as filled-in rectangles generally hanging under the second line from the top of a musical staff, though
Mensural notation and short notes (minims and crotchets), or groups of three short notes. In the 13th century, all of these were notated using only the longa and breve notes. A longa was automatically understood to fill a whole ternary metric group whenever it was in the neighborhood of other notes that did the same, i.e., whenever it was followed either by another longa or by a full group of three breves. When, however, the longa was preceded or followed by a single breve, then both filled a ternary group together. Thus, the longa had to be reduced to a value of