Object, see Direct object, Indirect object, Complement.
Obligation, 247, (moral) 247.
Opposites, formation of, 67; of "pli" and "plej", 80.
Opposition, distinguished from accompaniment, p. 49, ftn.
Order, of word endings, p. 10, ftn.; see also Position.
Ordinal numerals, 149; advs., 158; abbreviation of, p. 107, ftn.
Orthography, of proper nouns, 128.