impossible action
impossibility
alt-
unusable
possibility
possible action
opening
inexhaustible
unlimited
nonessential
soft option
out of service
inessential
Scotch mist
want
unblessed
need
non-prerequisite
high-hanging fruit
nontradable
onstream
researchy
at command
drug on the market
unworkable
substitutable
choosable
impractical
nonexistent
nonstandard
nonrecyclable
inappositely
nonexample
chrestomathic
forbidden fruit
unnecessity
unavoidable
fact of life
alternate
compatible
inadmissibility
sidegrade
nonfungible
pack-away
anthropotropic
between the devil and the deep blue sea
nonchallenge
nonexperience
unchewable
disposable