_astrum_.
1. _Stellae_, _sidera_, and _astra_ differ from one another. For
_stella_ is any separate star. _Sidera_ are made of very many stars,
as Hyades, Pleiades. _Astra_ are large stars as Orion, Bootes. But
the writers confuse these names, putting _astra_ for _stella_ and
_stella_ for _sidera_.[273]
[273] Isidore does not observe the distinctions he lays down
here. He does not seem to have known that Orion and Bootes were
constellations.