A (plural: pili ) is a hair-like appendage found on the surface of many bacteria and archaea . Derived from the Latin word for "hair," these proteinaceous filaments are critical for bacterial interaction with their environment and other cells. While they resemble tiny hairs, they are not used for locomotion like flagella; instead, they facilitate attachment, genetic exchange, and even a unique form of movement called "twitching motility". Essential Pili Vocabulary
To understand the role of pili in microbiology, it is helpful to master these key terms: Biology LibreTexts 2.5C: Fimbriae and Pili - Biology LibreTexts vocab pilus