cible
reducible
reflexible
refrangible
remissible
reprehensible
resistible
responsible
reversible
revertible
risible
seducible
sensible
tangible
terrible
transmissible
visible

In all other cases use _-able_.

III

The following nouns end in _-er_.

abetter
abstracter
accepter
adapter
adviser
affirmer
aider
almoner
annoyer
arbiter
assenter
asserter
bailer
caster
censer (vessel)
concocter
condenser
conferrer
conjurer
consulter
continuer
contradicter
contriver
convener
conveyer
corrupter
covenanter
debater
defender
deliberater
deserter
desolater
deviser
discontinuer
disturber
entreater
exalter
exasperater
exciter
executer (_except in law_)
expecter
frequenter
granter
idolater
imposer
impugner
incenser
inflicter
insulter
interceder
interpreter
interrupter
inviter
jailer
lamenter
mortgager (_except in law_)
obliger
obstructer
obtruder
perfecter
perjurer
preventer
probationer
propeller
protester
recognizer
regrater
relater
respecter
sailer (_ship_)
sorcerer
suggester
supplanter
upholder
vender

The following nouns end in _-or_.

abbreviator
abductor
abettor (_law_)
abominator
abrogator
accelerator
acceptor
accommodator
accumulator
actor
adjudicator
adjutor
administrator
admonitor
adulator
adulterator
aggregator
aggressor
agitator
amalgamator
animator
annotator
antecessor
apparitor
appreciator
arbitrator
assassinator
assessor
benefactor
bettor
calculator
calumniator
captor
castor (_oil_)
censor
coadjutor
collector
competitor
compositor
conductor
confessor
conqueror
conservator
consignor
conspirator
constrictor
constructor
contaminator
contemplator
continuator
contractor
contributor
corrector
councillor
counsellor
covenantor (_law_)
creator
creditor
cultivator
cunctator
debtor
decorator
delator (_law_)
denominator
denunciator
depredator
depressor
deteriorator
detractor
dictator
dilator
director
dissector
disseizor
disseminator
distributor
divisor
dominator
donor
effector
elector
elevator
elucidator
emulator
enactor
equivocator
escheator
estimator
exactor
excavator
exceptor
executor (_law_)
exhibitor
explorator
expositor
expostulator
extensor
extirpator
extractor
fabricator
factor
flexor
fornicator
fumigator
generator
gladiator
governor
grantor (_law_)
habitator
imitator
impostor
impropriator
inaugurator
inceptor
incisor
inheritor
initiator
innova