| Term | Definition |
| inherent | intrinsic, built-in, natural |
| inception | onset, debut, opening |
| justify | defend, show just cause, give good reasoning |
| intervene | interfere, meddle, intrude |
| ingenious | brilliant, inventive, creative |
| intrepid | daring, courageous, gutsy |
| instigate | provoke, incite |
| innovation | novelty, alteration, new wrinkle |
| irony | contradict, paradox |
| jeoparize | risk, compromise |
| indigent | destitute, penniless, poverty-stricken |
| judicous | prudent, discriminating, shrewd |
| insuperable | insurmountable, overwhelming, unconquerable |
| inveigh | denounce, berate, lambaste |
| jettison | dump, throw out, toss out |