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Showing content from https://www.nzplants.auckland.ac.nz/en/about/ferns/structure/frond.html below:

Frond - The University of Auckland

(photo, I MacDonald)

Loxogramme dictyopteris - These fronds are undivided (not divided into leaflets).

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Divided fronds: pinnate, bipinnate

Illustration: T.N.H. Galloway

Most ferns have divided fronds. These may be once-cut (pinnate), twice cut (bipinnate), three times cut (tripinnate and so on. The terminology used is as follows: stipe - the stalk or base of the frond rachis - the continuation of the stipe into the blade blade (lamina) - photosynthetic portion of the frond pinna, (pl, pinnae) or leaflet- a segment of the leaf blade

Once divided or pinnate frond

(photo, I MacDonald

Microsorum novae-zelandandiae - The frond midrib (rachis) bears a row of primary pinnae (leaflets).

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Twice divided or bipinnate frond

(photo, I MacDonald)

Deparia petersenii - The frond rachis bears a row of primary pinnae (leaflets) which have in turn been divided into secondary pinnae.

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(photo, I MacDonald)

Gleichenia alpina, alpine tangle fern - The midrib (rachis) of a single frond branches several times with each tier of branches forming leaflets.

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The coiling of young fronds

(photo, L Jensen)

Cyathea medullaris, black tree fern, young frond with black hairs and scales - In nearly all ferns the young leaves are coiled (circinate) and are commonly referred to as "fiddleheads".