Hello, you have come here looking for the meaning of the word onium. In DICTIOUS you will not only get to know all the dictionary meanings for the word onium, but we will also tell you about its etymology, its characteristics and you will know how to say onium in singular and plural. Everything you need to know about the word onium you have here. The definition of the word onium will help you to be more precise and correct when speaking or writing your texts. Knowing the definition ofonium, as well as those of other words, enriches your vocabulary and provides you with more and better linguistic resources.