Cocci (singular, coccus) are spherical prokaryotes. They occur singly, in pairs (diplococci), in chains (such as these streptococci), and in clusters like bunches of grapes (staphylococci).

Bacilli (singular, bacillus) are rod-shaped prokaryotes. They are usually solitary, sometimes the rods are arranged in chains (streptobacilli).

Spiral prokaryotes include spirilla, which range from comma-like shapes to long coils, and spirochetes (shown here), which are corkscrew-shaped.