Dicta is simply the plural of dictum. A dictum is a short, confident statement that someone — often a judge, a teacher, or a famous writer — puts forward as if it should be believed. One is a dictum; two or more are dicta. You will meet it in law and in serious essays far more than in daily talk. In court, a judge’s dicta can be interesting remarks that are not themselves the binding rule. English also allows dictums, which is easier; dicta keeps the Latin shape, the way some people still say cacti for more than one cactus. It is not a new word with a new meaning. If you already know dictum, you already know dicta.