| | ineffable | a. unutterable; cannot be expressed in speech | 
| inefficacious | a. not effective; unable to produce a desired result | 
| inequity | n. unfairness; lack of equity or abstract justice; disagreement with equitable principles | 
| inexorable | a. not capable of being swayed; unyielding; implacable | 
| inexplicable | a. difficult or impossible to explain or account for; not to be made plain or intelligible | 
| infidel | n. one who does not hold same religious beliefs as another | 
| infirmity | n. weakness; bodily ailment or weakness, especially one brought on by old age | 
| ingenue | n. an innocent, unsophisticated, naive young woman | 
| ingenuous | a. naive and trusting; young; unsophisticated | 
| ingrained | a. deeply established; firmly rooted | 
| ingratiate | v. become popular with; make agreeable or acceptable | 
| inhibit | v. restrain; prevent or forbid; hold back | 
| inimical | a. unfriendly; hostile; harmful; detrimental | 
| inimitable | a. matchless; not able to be imitated | 
| iniquitous | a. wicked or sinful; immoral; unrighteous | 
| insalubrious | a. unwholesome; not healthful; not promoting health | 
| inscribe | v. write or engrave; mark down as something to be read; imprint; assign or address to | 
| inscrutable | a. difficult to fathom or understand; impenetrable; mysterious | 
| insensate | a. lacking sensibility and understanding; foolish | 
| insensible | a. unconscious; unresponsive; very small or gradual | 
 |