المتين
كلمة (المتين) في اللغة صفة مشبهة باسم الفاعل على وزن (فعيل) وهو...
A person who is not competent for religious assignments.
A "qaasir" (minor) is any person who is not legally accountable and has not attained maturity of mind, like a fetus, a child, a mentally-disturbed person, an insane person, and the like. He is either lacking competence completely, such as a little child or an insane person, or lacking it partially, such as a discerning child. Competence means a person's qualification to be entitled to his rights and to be responsible for fulfilling the rights that are due upon him to others, which is called "competence for obligation and entitlement", or his qualification to perform actions, which is called "competence for performance".
"َQaasir": one incapable of doing something. Original meaning of "qusoor": not reaching the end. Other meanings: insane person, such as a child, a mentally-deficient, or a maniac.