The term 'involving more than one' can be summarized with the word 'PLURAL, ' which is a six-letter word. PLURAL refers to a word or phrase that denotes more than one person, place, thing, or idea. PLURAL forms of words are often indicated by adding an 's' or 'es' to the end of the word. For example, the PLURAL form of the word 'CAT' is 'CATS.' PLURAL forms of words can also be indicated by changing the word's spelling or pronunciation. For example, the PLURAL form of the word 'MOUSE' is 'mice.'