The prefix pseudo- (from Greek ψευδής "lying, false") is used to mark something as false, fraudulent, or pretending to be something it is not.
In biology and botany taxonomy the prefix 'pseudo' or 'pseud' can indicate a species with a visual similarity to another genus. An example is the Iris species Iris pseudacorus, by having leaves similar to those of Acorus calamus in the Acorus genus, having pseud—acorus ('false-acorus') in its botanical name.