Expressing an opinion is a fundamental part of communication. It involves expressing one's thoughts and feelings about a certain topic or issue. OPINE, VOICE, and SPEAKUP are all words that can be used to express an opinion. OPINE means to express an opinion or belief, while VOICE is to express one's opinion or feelings in words. SPEAKUP is to express one's opinion or feelings openly and without fear. All three words can be used to express an opinion in different ways.