The Hebrew word מוֹפֵת (mophet) occurs in Scripture 36 times. It is one of several words meaning “wonder, sign, miracle.” The assumed root isאפת (defined in TWOT* as “wonder, miracle, sign, portent”). We say this is the assumed root because “no verb or other noun uses the same root letters… however, the meaning of môpēt is not questioned” (ibid.).
TWOT also observes, “The first occurrences of môpēt in the OT are in Ex 4:21; 7:3; 11:9-10. In these verses it refers to Moses’ rod changing into a snake (7:9), as well as to the ten major plagues on the Egyptians.
*TWOT is the abbreviation for standard Bible reference work Theological Wordbook of the Old Testament (2 vols.; Chicago: Moody Press, 1981).