Annulus: ring of dead cells found around spores
Attenuate: Gradually tapering to a very slender point
Bipinnate: Doubly or twice pinnate
Dimorphic: Having two forms
Frond: the leaf of a fern
Indusium (plural= indusia): a protective membrane on developing spores
Pinnae (singular= pinna): the "leaflets" of fern fronds ("leaves")
Pinnate: Compound, refers to divided features arising from an axis (the rachis in ferns)
Pinnatifid: Pinnately cleft, having no lobes or lobes that do not reach the rachis
Pinnule: A secondary pinna ("sub-leaflets")

Rachis: The upper part of the fern petiole, where the pinnae are found
Radial: Growing in a cirlce or wheel-like pattern
Rhizome: underground stem part of the fern, usually is horizontal
Sorus (plural= sori): cluster of sporangia
Sporangium (plural= sporangia): organ which produces spores
Sterile: In ferns, refers to a frond or pinna which has no reproductive parts
Stipe: The stalk below the blade in ferns
Ternate: Arranged in threes