Grief, melancholy, regret, sadness, sorrow.
Hale, healthful, healthy, salutary, sound, vigorous.
Ignorant, illiterate, uninformed, uninstructed, unlettered, untaught.
Impulsive, involuntary, spontaneous, unbidden, voluntary, willing.
Indispensable, inevitable, necessary, requisite, unavoidable.
Inquisitive, inquiring, intrusive, meddlesome, peeping, prying.
Intractable, perverse, petulant, ungovernable, wayward, wilful.
Irritation, offence, pique, resentment.
Probably, presumably.
Reliable, trustworthy, trusty.