what is the trait you would use to a fish as belonging to either the phylum chordata or the phylum arthropada
No it is not. It is either grandparent's (belonging to one grandparent) or grandparents' (belonging to more than one of them).
The vegetables can be classified as either dicots or monocots.
Hybrids are a mix of two different species. It is difficult to classify hybrids because they do not fit into either specific species.
Earum or illarum is one Latin equivalent of 'belonging to them'. Either may be used when the owner is feminine. Eorum or illorum is another Latin equivalent. Either may be used when the owner is masculine.
There are either special-purpose or general purpose computers.
See if they have cell walls
because either the borders or the language spoken there is the other one
Time is either linear or circular. Make your choice.
Moon Over Manifest is a historical fiction book, although you could classify it as mystery, as well. Either genre is appropriate, and many people classify it as both genres.
I think you got the spelling wrong, and it is "Chordates(phylum Chordata) are animals which are either vertebrates or one of several closely related invertebrates."
Davinci's dick is primary and yours is lucky to be secondary
Moon Over Manifest is a historical fiction book, although you could classify it as mystery, as well. Either genre is appropriate, and many people classify it as both genres.