the number of overlaps; fold, layer

need, necessity / essential

key, important point / essential piece of something, requirement

the pin or rivet holding the spines of a folding fan together / (by extension) a pivot, cornerstone, keystone / a pin, often decorated, holding the handle to the tang of a katana

a female given name

(archaic, possibly obsolete) the pin or rivet holding the spines of a folding fan together

(archaic, possibly obsolete) fortress, redoubt / (archaic, possibly obsolete) important point, key

柔軟性: flexibility

十二月, 12月: December

十月, 10月: October