A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to.
In the case of certain orchids and cacti, it denotes a round nodule, small eminence, or warty outgrowth found on the lip. They are also known as podaria (singular podarium). When referring to some members of the pea family, it is used to refer to the wart-like excrescences that are found on the roots.
In mycology, a tubercle is used to refer to a mass of hyphae from which a mushroom is made.
When it is used in relation to certain dorid nudibranchs such as Peltodoris nobilis, it means the nodules on the dorsum of the animal.
These tubercles in nudibranchs can present themselves in different ways : each tubercle in a single rounded, conical or angular form, each tubercle in a compound form of two or more levels, tubercles in amalgamated clusters or as tubercles forming or joined by a ridge.
In dinosaurs, a tubercle is a general term for the scales seen in skin impressions. In duck-billed dinosaurs, for example, three main types of tubercles are defined: small tubercles with no definite arrangement (ground tubercles); larger, polygonal tubercles (pavement tubercles) up to 1 cm (0.4 in) in diameter, which are grouped into clusters separated by ground tubercles; and limpet-shaped conical scutes.