| inborn(adjective, basic, absolute, fundamental, key) |
| inbred(adjective, basic, absolute, fundamental, key) |
| income(noun, essence, profit, core, outcome) |
| indispensable(adjective, important, original, essential, critical) |
| indispensable content(noun, expression, essence, profit, core) |
| indisputable fact |
| inescapable fact |
| infallibility(noun, certainty, principle, fact, reality) |
| innards(effect, meaning, essence, import, gist) |
| innate(adjective, basic, absolute, fundamental, key) |
| inner essence |
| inside track(noun, expression, certainty, principle, fact) |
| integral(important, essential, critical, basic, fundamental) |
| intendment(noun, good, understanding, point, burden) |
| interpretation(noun, good, understanding, point, burden) |
| intimation(noun, understanding, effect, sense, subject) |
| intrinsic(adjective, original, basic, absolute, fundamental) |
| item(noun, feature, part, plan, point) |
| key(adjective, important, essential, critical, basic) |
| key point(noun, expression, essence, profit, core) |