[Mollusca] The chitinous, ribbon-like band in the mouth of molluscs containing numerous transverse rows of teeth.
- ctenodont: A radula in which the rachidian (central) and lateral teeth are similar in appearance; each has multiple cusps (more than three). The central cusp (mesocone) on the rachidian tooth may be inconspicuous.
- heterodont: A radula in which the teeth on each side are different from one another in appearance; the rachidian tooth has one or two cusps on either side of a distinct central cusp (mesocone), and each lateral tooth bears one or two cusps.
- homodont: A radula in which all teeth appear similar in size and shape; each rachidian and lateral tooth has one simple cusp.

[Pteropoda] Series of chitinous teeth in the buccal mass used in catching prey (Radula teeth, Pneumodermopsis in ventral view, Clione in ventral view, Spongiobranchaea austr. radula). The first, or the additional last lateral teeth are sometimes different from the others. The additional (a), lateral (l), modified lateral (ml) and median (m) teeth are expressed in a radula formula as: (a)-l-(ml)-m-(ml)-l-(a); some examples of radula formulae are: Limacina: 1-1-1; Cavolinia: 1-1-1; Peraclis: (1)-1-1-1-(1); Pneumodermopsis: 6-1-6; Pneumoderma: 1-0-1; Thliptodon: 3-(1)-1-(1)-3; and Clione: 15-1-15.

[Cephalopoda] The chitinous ribbon-like band in the mouth of cephalopods containing numerous transverse rows of teeth (Ce 1P, Ce 1Q). Absent in Spirula and most cirrate octopods.

Alternative forms for Radula : ctenodont, heterodont, homodont.