also: おやゆびたいこうせい
opposable thumb; thumb opposition
Medical/anatomical term referring to the ability of the thumb to touch the fingertips, a key feature of primate hands.
The opposable thumb in humans is an important feature that enabled tool use.
母指対向性の喪失は、日常生活に大きな支障をきたす。
Loss of thumb opposition causes significant difficulty in daily life.