Nearly every Ukrainian understands Russian, but many Russians would only understand the gist of what Ukrainians are saying, because the languages only share about 60% of their vocabulary.
A lot of common, everyday words differ in Ukrainian and or arise from different roots (e.g Polish).
> Oh no, only 60%? Surely that's plenty for a conversation, no?
It's plenty for communication, not plenty for a conversation.
(It's also a mirror for colonialism, by the way, where the occupied speak the language of the occupier, but the occupiers can't be arsed to learn the language of the occupied.)
It's not even necessarily enough for communication. With the Pareto curve on word commonality it's really quick to get high percentages of vocabulary. But it's the words you don't know on a sentence that are usually the important ones.
A lot of common, everyday words differ in Ukrainian and or arise from different roots (e.g Polish).