I remember this from a while back to remember the requirements for 3rd normal form. I thought I’d pass it along in case it helps.
“The key, the whole key and nothing but the key, so help me Codd.”
“the whole key” - meaning non key columns shouldn’t have a partial dependency (depending on a subset of the key columns)
“nothing but the key” - meaning non key columns should only depend of the key, not on another non-key column (i.e. transitive dependency).