Immutable
Unchangeable, permanent
Impartial
Fair, unbiased, neutral
Inadvertent
Accidental
Incessant
Unceasing, never-ending; usually implies an unpleasant condition
Incoherent
Jumbled, hard to understand
Incongruous
Inconsistent or inappropriate
Indifferent
Not caring one way or the other; can also mean “mediocre”
Indulgent
Lenient, giving in to momentary desires or whims
Inevitable
Unavoidable, especially when referring to a result of a course of action or decision
Infamous
Having a bad reputation; disgraceful
Innate
Inborn, inherent
Innocuous
Harmless, insignificant
Insipid
Dull, meaningless, empty
Irascible
Irritable
Ironic
Marked by an unexpected difference between what might be expected and what actually happens, using words so as to convey the opposite of their literal meaning; satiric
Laudable
Worthy of praise
Lax
Careless, negligent, not diligent
Lucid
Clear, easily understandable
Marred
Damaged or scarred
Novel
New or original
Objective
Without bias, analyzing logically based on facts
Obscure
Unclear, clouded, partially hidden; hard to understand
Orthodox
Conventional, adhering to established principles or practices, especially in religious matters
Pedestrian
Common, ordinary
Peripheral
Unimportant, of little consequence
Pervasive
A quality of being present throughout; permeating
Pious
Reverent or devout, depending on context, can also mean falsely devout
Pivotal
Crucial, result changing
Pragmatic
Practical, based on experience rather than theory
Pretentious
Pompous, self-important
Prodigal
Extravagant, rebellious, wasteful
Prodigious
Enormous, of extraordinary size
Profound
Deep, insightful
Profuse
Extravagant, free-flowing
Prosaic
Dull, unimaginative
Provincial
Limited in outlook to one’s own small area; narrow; implies the provincial person also thinks that the rest of the world is just like his or her limited experience
Provocative
Exciting; attracting attention or sparking controversy
Prudent
Careful, wisely cautious