This comment is correct, I've heard the property described as "probabilistic consensus".
However, this part is wrong:
> Because of finite propagation delays and network packet loss, there are normally multiple valid chains at any given moment in time.
How often forks occur is a property of a specific system, not of "blockchain" in general. Bitcoin, for instance, usually does not have multiple chains. They do sometimes happen but generally the orphan rate is quite low. Ethereum has a much higher block rate so propagation delays are more important and forks happen there much more often.
There's an improvement called Bobtail [1] which makes the network much better at estimating how much work has been done. A blockchain which adopted Bobtail would still have probabilistic consensus but would almost never have forks.
Casper, Ethereum's proposed Proof of Stake system, is designed to provide "finality", what the rest of us call "consensus". Once adopted, and assuming it works, we'll have a blockchain where you can be sure that every block you see which you determine is valid is a block which the rest of the network will also decide is valid (assuming less than 1/3 of the network is byzantine).
However, this part is wrong:
> Because of finite propagation delays and network packet loss, there are normally multiple valid chains at any given moment in time.
How often forks occur is a property of a specific system, not of "blockchain" in general. Bitcoin, for instance, usually does not have multiple chains. They do sometimes happen but generally the orphan rate is quite low. Ethereum has a much higher block rate so propagation delays are more important and forks happen there much more often.
There's an improvement called Bobtail [1] which makes the network much better at estimating how much work has been done. A blockchain which adopted Bobtail would still have probabilistic consensus but would almost never have forks.
Casper, Ethereum's proposed Proof of Stake system, is designed to provide "finality", what the rest of us call "consensus". Once adopted, and assuming it works, we'll have a blockchain where you can be sure that every block you see which you determine is valid is a block which the rest of the network will also decide is valid (assuming less than 1/3 of the network is byzantine).
[1] https://arxiv.org/abs/1709.08750