Eighth notes
Section outline
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In swing rhythm, the pulse is divided unequally, such that certain subdivisions (typically either eighth note or sixteenth note subdivisions) alternate between long and short durations. In shuffle rhythm, the first note in a pair may be twice (or more) the duration of the second note. In swing rhythm, the ratio of the first note's duration to the second note's duration can take on a range of magnitudes.(Wikipedia)
Example of eighth notes:

The quarter note is usually shortened like this:
