Merriam-Webster's Collegiate Dictionary:
inferrer
inferrible
infertile
infertility
infest
infestant
infestation
infester
infibulation
infidel
infidelity
infield
infield hit
infield out
infielder
infight
infighter
infighting
infiltrate
infiltration
infiltrative
infiltrator
infinite
infinitely
infiniteness
infinitesimal
infinitesimal calculus
infinitesimally
infinitival
infinitive
infinitively
infinitude
infinity
infirm
infirmary
infirmity
infirmly
infix
infixation
infl
inflame
inflamer
inflammability
inflammable
inflammableness
inflammably
inflammation
inflammatorily
inflammatory
inflammatory bowel disease
inflatable
inflate
inflated
inflater
inflation
inflationary
inflationary spiral
inflationism
inflationist
inflator
inflect
inflectable
inflection
inflection point
inflectional
inflectionally
inflective
inflexed
inflexibility
inflexible
inflexibleness
inflexibly
inflexion
inflict
inflicter
infliction
inflictive
inflictor
inflorescence
inflow
influence
influenceable
influent
influential
influentially
influenza
influenzal
influx
info
infobahn
infold
infomercial
inform
informal
informality
informally
informant
