achenoid

Achenoid is a botanical term used to describe fruit-like structures that resemble an achene but do not meet all formal criteria of a true achene. The word is formed from the suffix -oid meaning "resembling" and the noun achene, a dry, single-seeded fruit typical of several plant families such as the Asteraceae. In practice, an achenoid is described in floras and taxonomic notes to convey similarity to an achene while noting a distinguishing feature that prevents classification as a true achene. In many cases an achenoid is a small, dry, indehiscent body containing a single seed, with the pericarp not fully separated from the seed coat, or with pericarp tissue at least loosely attached to the seed.

Because the term is not standardized and is used variably by authors, its exact definition can differ between treatments. Some botanists prefer the more explicit term "achenoid" or simply "achene-like fruit" when describing structures that are superficially similar to an achene but botanically distinct. The concept is most often encountered in morphological descriptions rather than as a formal taxonomic category.

Examples are not uniformly cited, but achenoids are commonly referenced in plant groups where fruit morphology is highly variable and where precise fruit boundary definitions aid comparative descriptions. For practical purposes, "achenoid" signals a resemblance to an achene while signaling that the fruit does not conform to the conventional technical criteria of achenes.