What is the difference between a 'living' and 'dead' virus, since viruses are technically never 'living'?

Excellent point: It is true that viruses are not living. They are strands of dna wrapped in a protein coat. A more accurate term would be a whole virus (which can infect and cause symptoms) and a partial virus or viral particle (which could help the body develop an immune response without getting the symptoms of the whole virus.).

Ability to infect: A live virus is able to infect a cell and hijack it in order to produce more viruses. A "dead" virus (perhaps more accurately called an inactivated virus) is unable to function and incite a cell to make more copies of it.