Eli5: what exactly is a virus and are viruses alive?

I feel like discussions on viruses too often end up on "well technically they're not living" and it's like, even non-technically, there's very little about them that anyone would consider life-like.

They don't have cells, which means they don't have organelles (biology term of "thing that does stuff") which means they can't do...anything. Like they just kind of passively...sit there...never doing anything. They don't move; they don't sense. They don't even really die any more than you could say that a baseball is capable of dying.

But they just happen to have some proteins in/on them structured in precisely the right way, such that, if they were coincidentally to happen to bump into a cell, they would break through the cell walls and start causing havoc. And the havoc they would cause just coincidentally happens to be exactly the right havoc to get the cell to make a million more mostly-exact copies of the virus.

/r/explainlikeimfive Thread Parent