built-in
constitutional
inbuilt
inherent
inner
integral
internal
intimate
actual
appropriate
basic
central
characteristic
congenital
connate
deep
deep-seated
distinctive
distinguished
elemental
esoteric
essential
fundamental
genuine
hereditary
idiocratic
idiosyncratic
immanent
implanted
implicit
in character
inalienable
inborn
inbred
indoor
indwelling
infixed
ingrained
inherited
inmost
innate
innermost
inside
interior
intestine
inward
inwrought
intrinsicality
ethical
extrinsic
physical
structural
transcendent
ultimate
undeniable
undoubted