noun
flat feet; flatfoot; splayfoot
Medical term for a condition where the arch of the foot is flattened, causing the entire sole to touch the ground. Used in both clinical and everyday contexts.
彼は扁平足なので、長時間立っていると足が痛くなる。
He has flat feet, so his feet hurt when he stands for a long time.
扁平足の人は、足の裏全体が地面につく。
People with flat feet have the entire sole of their foot touching the ground.