4.5: Tuplets
Tuplet is a generic term that describes a grouping of notes that would not normally occur within a beat.
A quarter note naturally divides into two eighth notes or four sixteenth notes. A triplet is a grouping of three eighth notes that occurs within the span of the quarter note. A quintuplet would be a grouping of five sixteenth notes to occur within the span of one quarter note. It is not uncommon to see quintuplets, sextuplets, and septuplets.
If you write a piece of music that naturally has a triplet division to the beat, you should use 68, 98 or 128 depending on the number of beats in each measure.
In compound meter, a duplet is a grouping of two eighth notes to occur within the span of a dotted quarter note and a quadruplet is a grouping of four eighth notes to occur with the span of a dotted quarter note.