You shouldn't have gone there into passive voice.

sis. it's been a while since a read that and had that class so i can't answer for u

- "the basic difference between keywords and subjects is that subjects (or "subject headings") have been predetermined, while keywords have not. a keyword is an easy place to start because you can use any word that seems to fit your search; this is called "natural language" searching."

i think its descriptve symbols but im not sure