意見を吐く
いけんをはく to give one's opinion

意見を持つ
いけんをもつ to hold an opinion

意見を言う
いけんをいう to state one's opinion

意見交換
いけんこうかん exchange of ideas exchange of opinions

意見広告
いけんこうこく protest advertising (on an issue by a pressure group)

意見書
いけんしょ opinion in writing written opinion argument