| inherent(adjective, characteristic, close, start, natural) |
| innate(adjective, characteristic, start, natural, fixed) |
| ingrained(adjective, characteristic, start, natural, fixed) |
| essential(adjective, characteristic, physical, material, important) |
| inborn(adjective, characteristic, start, natural, fixed) |
| congenital(adjective, characteristic, start, natural, fixed) |
| native(adjective, start, natural, basic, instinctive) |
| interior(adjective, heart, secret, private, mental) |
| natural(adjective, start, basic, inside, instinctive) |
| inner(adjective, characteristic, essential, intimate, private) |
| internal(adjective, characteristic, close, natural, heart) |
| inbred(adjective, characteristic, start, natural, fixed) |
| inward(adjective, close, private, mental, inner) |
| deep-seated(adjective, characteristic, natural, original, fixed) |
| rooted(adjective, impulse, inside, instinctive, interior) |
| visceral(adjective, natural, heart, secret, private) |
| constitutional(adjective, characteristic, close, start, important) |
| fundamental(adjective, characteristic, important, significant, natural) |
| intuitive(adjective, natural, mental, instinctive, automatic) |
| intimate(adjective, characteristic, close, heart, affected) |