Rodlike

Rodlike is an adjective used to describe objects whose shape is elongated and cylindrical, with a length appreciably greater than the width. The term is common in biology, microbiology, geology, and materials science to convey a body plan that is not spherical or twisted.

In biology, many bacteria are described as rod-shaped, a form known as bacillus. Examples include Bacillus subtilis and Escherichia coli. The rod shape increases the surface area–to–volume ratio, influencing nutrient uptake and cell-wall structure, which in bacteria is largely peptidoglycan. Rod-shaped bacteria may be motile, often by flagella, or non-motile. Some species can alter their morphology in response to environmental conditions, switching to coccoid forms when stressed.

Outside microbiology, rodlike describes slender crystalline or particulate forms, including acicular crystals and nanorods. In nanotechnology, nanorods are nanoscale rodlike particles with high aspect ratios, used in optics, electronics, and catalysis (examples include gold nanorods and ZnO nanorods).

The concept of rodlike morphology helps categorize shapes in taxonomic descriptions, ecological studies, and materials design, reflecting how form relates to function in diverse systems.