Filamentation (see "filament") is the anomalous growth of certain bacteria, such as E. coli, in which cells continue to elongate but do not divide (no septa formation). Bacterial filamentation is a defect in completing replication and is observed in bacteria responding to a various stresses. This may happen, for example, while responding to extensive DNA damage through the SOS response system.

breakage of filaments, resulting in the creation of a fibrous or hairy appearance on the surface of a yarn package or fabric.