The Bible is well known for its ellipsis* and its lack of explanatory statements of a term used. There are exceptions in grammatical patterns, such as John exclusively using Archon for ruler in his writings - which make the term self evident.
Sin - is defined
"One" (unity) - is somewhat defined and also self evident from the context (no exceptions, every person part of that unity is listed in the context)
An interesting thing to see would be how many terms are actually used and explained
*the omission from speech or writing of a word or words that are superfluous or able to be understood from contextual clues.