I wanted to know if there is a noun stating the following: "state of being 10, 27, etc years old." For example, consider the sentences "He is 10 years old and because of that, he is happy." I want to say that "X makes him happy" and by X I mean the state of being 10 years old. Another example is: "X is one of the best periods of a human's life" or "After X becomes Y," which by Y I mean "being 11 years old." I hope I were clear enough about my question.
Actually, I am looking for a word like "5 years old-ness." As a matter of fact, I want to make a literary sentence. I want to say: "I was standing near my 'being 10' in my dream," and I don't want to mention that "being 10" is an object or a human. I want it to be an abstract noun. For example, we have the word "forties" which shows the person is aged between 40 and 49 and we have phrases such as early/mid/late forties. I want to know if there is such a word or phrase for "being 10 years old." Cheers