title_body: Do constructed languages need to have their own letters, words, & sounds? In order for me to ask a higher quality question, I need to know, do constructed languages need to have their own letters, words, &amp; sounds?
upvoted_answer: No, a conlang does not need any of it. You can construct a language based on gestures (a sign language) or on whistles, or on other signals transporting information. You can construct a Pasigraphy, i.e., a written-only language.
  
  But for a more conventional design that meets our intuition of language, you will probably use sounds and words, and letters to write the language. It is up to your creativity to come up with original sounds and letters, but there is definetely no need to do so. Many conlang designs rely on sounds (and complete phonologies) that occur in natural languages, and use usual letters (mostly Latin, but also Cyrillic or other existing writing systems like Runes) for writing. The words of a conlang are most often original but I even can imagine a conlang without original words: Draw existing words for natural languages in an eclectic way or create a conlang closely based on a natural language or a group of natural languages. The vocabulary of IALA Interlingua is hardly original.