Motivic Transformation (rhythm alone) Theory Things   William Wieland
I provided only one example of augmentation, diminution, extension and truncation. Many are possible.
Original Motive:(a musical word)
Augmentation:(multiplication—in this case, twice as long)
Diminution:(division—in this case, half as long)
Extension:(addition—Think hair extension. You have the original and you simply add a little more.)

(or Truncation)

P.D.Q. Bach (Peter Schickele) - "New horizons in music appreciation" (Beethoven)   (YouTube)

    1:55 — Motif = Motive ( short–short–short—long )

    2:21 — The motive is extended. ( short–short–short—long—long—long )

    3:50 — The motive is truncated or fragmented (broken up into little pieces).