Letters that make nonobligatory
a, o, b, g, l, n, r, t, i, y are letters that make 'nonobligatory'
Words within nonobligatory
gat, OR, OB, Tory, obligato, nob, at, Ono, non, obligatory, on, li, no, gator, Ob, tor, At, Ga, Li, No, Ig, IgA, GA are words within 'nonobligatory'