Ramen noodles are called chūkamen (中華麺), which means "Chinese noodles," derived from traditional Chinese alkaline noodles. They are typically made from wheat flour, salt, water, and a special alkaline mineral water called kansui (a mixture of sodium carbonate and potassium carbonate). Kansui gives the noodles their characteristic yellowish color, firm texture, and springiness. Ramen noodles can vary in shape and thickness; they may be thick, thin, ribbon-like, straight, or wrinkled. Unlike other Japanese noodles such as udon, soba, or somen, ramen noodles specifically contain kansui, which is the defining ingredient. In summary, the noodles in ramen are wheat-based alkaline noodles made using kansui, which distinguishes them from other types of noodles used in Japanese cuisine.