Worship is adoration and honor of the sort that is due only to that one Being who created us. Adoration is the acknowledgment of God as God, Creator and Savior, the Lord and Master of everything that exists.
Veneration is showing devotion and respect that is befitting to rational creatures who by their extraordinary example of virtue show us how to follow God.
We do not venerate God, for that would treat God like a creature. Nor do we worship or adore any saint, for that would treat a mere creature like God.
-A8
The thesaurus and the dictionary give us definitions of words.
They use veneration and worship interchangeably.
I'm more interested in the acts that are taking place when one venerates and/or worships.
If the acts are the same, or substantially the same, then the burden is on the actor to demonstrate the distinction (s)he sees.
For example, in praying to Mary, since Mary is not omniscient or omnipresent, how exactly are these prayers heard?