Traditionally, shoes have been made from leather, wood or canvas, but in the 2010s, they are increasingly made from rubber, plastics, and other petrochemical-derived materials.
Dress shoes are characterized by smooth and supple leather uppers, leather soles, and narrow sleek figure. Casual shoes are characterized by sturdy leather uppers, non-leather outsoles, and wide profile.
Though the human foot is adapted to varied terrain and climate conditions, it is still vulnerable to environmental hazards such as sharp rocks and temperature extremes, which shoes protect against. Some shoes are worn as safety equipment, such as steel-soled boots which are required on construction sites.
Units for shoe sizes vary widely around the world. European sizes are measured in Paris Points, which are worth two-thirds of a centimeter. The UK and American units are approximately one-quarter of an inch, starting at 8¼ inches. Men's and women's shoe sizes often have different scales.