- in loco parentis
- in love
- in low spirits
- in name
- in name only
- in no time
- in on
- in one case
- in one ear
- in one's birthday suit
- in one's own right
- in operation
- in order
- in other words
- in particular
- in passing
- in perpetuity
- in person
- in place
- in play
- in point of fact
- in practice
- in principle
- in private
- in public
- in question
- in reality
- in return
- in secret
- in series
- in short
- in short order
- in sight
- in situ
- in small stages
- in so far
- in some manner
- in some way
- in someone's way
- in spades
- in spite of appearance
- in stages
- in stock
- in store
- in straitened circumstances
- in stride
- in style
- in tandem
- in that
- in that location
- in that respect
- in the adjacent apartment
- in the adjacent house
- in the air
- in the altogether
- in the bargain
- in the beginning
- in the buff
- in the end
- in the first place
- in the flesh
- in the lead
- in the least
- in the long run
- in the lurch
- in the main
- in the meantime
- in the midst
- in the nick of time
- in the public eye
- in the raw
- in the same breath
- in the south
- in the way
- in their right minds
- in theory
- in this
- in time
- in toto
- in truth
- in turn
- in two ways
- in unison
- in use
- in utero
- in vacuo
- in vain
- in vitro
- in vivo
- in vogue
- in writing
- in your birthday suit
- inability
- inaccessibility
- inaccessible
- inaccessibly
- inaccuracy
- inaccurate
- inaccurately
- inachis
- inachis io
- inaction
- inactivate
- inactivation
- inactive
- inactiveness
- inactivity
- inadequacy
- inadequate
- inadequately
- inadequateness
- inadmissibility
- inadmissible
- inadvertence
- inadvertency
- inadvertent
- inadvertently
- inadvisability
- inadvisable
- inadvisably
- inaesthetic
- inalienable
- inalienably
- inalterable
- inamorata
- inamorato
- inane
- inanely
- inanimate
- inanimateness
- inanition
- inanity
- inanna
- inapplicability
- inapplicable
- inapposite
- inappositeness
- inappreciable
- inappropriate
- inappropriately
- inappropriateness
- inapt
- inaptitude
- inaptness
- inarguable
- inarticulate
- inarticulately
- inartistic
- inattention
- inattentive
- inattentively
- inattentiveness
- inaudibility
- inaudible
- inaudibleness
- inaudibly
- inaugural
- inaugural address
- inaugurally
- inaugurate
- inauguration
- inauguration day
- inauspicious
- inauspiciously
- inauspiciousness
- inauthentic
- in-basket
- in-between
- inboard
- inborn
- inborn error of metabolism
- inborn reflex
- inbound
- in-bounds
- inbred
- inbreeding
- inbuilt
- inc
- inca
- incalculable
- incalescence
- incan
- incandesce
- incandescence
- incandescent
- incandescent lamp
- incantation
- incapability
- incapable
- incapableness
- incapacitate
- incapacitated
- incapacitating
- incapacity
- incarcerate
- incarceration
- incarnadine
- incarnate
- incarnation
- incase