What shape does the term 'bacillus' refer to?

The term 'bacillus' specifically refers to a rod-shaped bacterium. In microbiology, classification of bacteria typically involves their shapes, which are fundamental characteristics for identifying different types. Bacilli (plural of bacillus) are elongated and cylindrical, resembling a rod, which distinguishes them from other shapes such as cocci (spherical) and spirilla (spiral). This rod shape is significant in various contexts, including how the bacteria move, how they reproduce, and their overall biology. Understanding these shapes helps in microbiological studies, including disease classification and treatment approaches, demonstrating why the term 'bacillus' is indeed associated with a rod-shaped structure.