gaster

Gaster is a term that appears in biology, anatomy, and popular culture with several distinct senses. It derives from the Greek gastēr, meaning stomach, and has come to denote the belly or abdominal region in various languages and scientific contexts.

In entomology and comparative anatomy, gaster refers to the posterior portion of the abdomen in many arthropods, especially insects such as ants and wasps. The body is typically divided into a head, thorax, and abdomen; the abdomen's rear part is often called the gaster, which contains much of the digestive and reproductive organs and, in several species, the venom apparatus. In ants, the gaster is the bulbous rear of the body beyond the petiole and postpetiole.

In broader medical and descriptive usage, gaster is connected to the stomach through the related prefixes gastric and gastro-, which are derived from the same ancient root. Modern English commonly uses these prefixes to describe stomach-related anatomy, disease, or procedures, rather than the standalone form gaster.

In popular culture, Gaster most notably refers to Dr. W. D. Gaster, a fictional and enigmatic scientist in the video game Undertale by Toby Fox. The character is introduced indirectly through in-game texts and lore and has inspired extensive fan speculation about the game's backstory and connections to other characters.

Overall, gaster is a flexible term whose primary technical sense is anatomical, signaling the posterior abdominal region in various organisms, while also appearing in language and fictional contexts.