When to use ac instead of et?

1. What is the difference between AC and ET in Latin?
2. What does the Latin word AC mean?

What is the difference between AC and ET in Latin?

Ac is a long syllable (I think), atque is two shorts (which is...odd, since there are two adjacent consonants) et is one short, and -que is one short (which is often elided).

What does the Latin word AC mean?

A.C. or A.C.N. From Latin Ante Christum or Ante Christum Natum, meaning "Before Christ" or "Before Christ (was) Born." B.C. and B.C.E.