المعنى الاصطلاحي :

What man does by his own choice to bring about benefit or ward off harm.

الشرح المختصر :

Man was created with powers and potentialities that render his inner self susceptible to both piety and impiety, and disposed to both good and evil. Allah gave man the mind to distinguish between truth and falsehood, and between good and evil. He gave him the ability with which he can do good and abandon evil, and He detailed the Islamic methodology for him. Therefore, as long as the discerning mind is present, the ability to act is intact, and the right methodology is clear, then the freedom of will and choice is affirmed for man. He must, thus, direct his powers towards the good or evil that he chooses for himself. Whatever emerges from the heart, tongue or body, of good or evil, is a result of his choices, and he is not compelled to do anything, as he acts out of his own accord, and if he wishes he can stop. He is not, however, the creator of his actions, because the slave, with his body, attributes, and actions, is a creation of Allah. Hence, his ability falls under the ability of Allah and his will falls under the will of Allah. He, thus, wills by the will of Allah, and is able by the ability of Allah, and it is the Lord, Glorified be He, who gave him free will and ability and taught him what benefits him and what harms him. He commanded him to use his will and ability to bring about goodness and abandon evil. So, if he uses them to bring about goodness and abandon evil, he is praiseworthy. Nonetheless, if he uses them in the opposite way then he is blameworthy. If a slave prays and fasts, then he is truly the one who prays and fasts. If he disobeys, then he is truly disobedient and immoral, because he has free will and ability.

التعريف اللغوي المختصر :

"Kasb": collecting, earning. Other meanings: what is obtained. Original meaning: seeking, striving.