əˈthirēəm noun
Usage: capitalized
Etymology: New Latin, irregular from Greek athoros without sperm (from a- a- (II) + thoros semen) + New Latin -ium; akin to Middle Irish dairim I leap upon, Sanskrit dhārā stream
: a genus of ferns (family Polypodiaceae) differing from Asplenium (in which it is often included) in having curved or lunate sori — compare lady fern