prefix Un
undo
do not do it, stop doing something you did
talk
talked
nonstop
to not stop
play
played
unpack
walk
walked
nonstick
does not stick
follow
followed
unstick
take out the stick, do not stick
jump
jumped
nonfat
no fat
fall
unhappy
not happy
smile
smiled
nonsense
does not make sense
stop
stopped
untrue
not true
stand
stood
nonfiction
not fiction
carry`
carried