objeto, m., object, purpose.
obligación, f., obligation.
obligado, -a, adj. pp. of obligar, obliged; necessary, unavoidable, indispensable, natural.
obra, f., work; matter; — de, at (or of) about, about; como — de, a matter of; about; poner por —, to carry out, execute.
obscurecer, to obscure, blind, darken, grow dark; refl., to grow dark, be (or become) dark; to go out.
obscuridad, f., obscurity, gloom.
obscuro, -a, dark, obscure.
observar, to observe.
obstáculo, m., obstacle.
obstante: no —, nevertheless, notwithstanding.