المعنى الاصطلاحي :

Confirmation or verification of something by mentioning the name of a glorified entity in a particular wording by using one of the Arabic letters of swearing.

الشرح المختصر :

"Yameen" (oath-taking) means confirming a ruling/statement by mentioning something glorified, preceded by one of the Arabic letters used for swearing or taking an oath. It is to swear by one of the names of Allah the Almighty or one of His attributes, joined with an Arabic letter used for swearing, which are the letters: "baa", "taa," and "waw." The secret behind the prohibition of swearing by other than Allah the Almighty is that swearing or taking an oath necessitates glorifying what one swears by. Since glorification is an exclusive right of Allah the Almighty, it is not permissible to swear by other than Him. Another reason for the prohibition is that swearing implies taking the one being sworn by as a witness to one’s truthfulness. This can be valid only if the witness knows whether the swearing person is truthful or not, and this can be none but Allah alone. Moreover, the entity by which one swears must possess the power to punish and avenge whoever swears by it falsely, and none can do this but Allah alone without any partner. Oath-taking is an act of worship that must not be dedicated to anyone other than Allah. Hence, it is impermissible to swear by other than Him. Whoever swears by other than Allah, whether it is a prophet, a righteous ally, the Ka`bah, or anything else, has indeed committed a major sin, and has fallen into polytheism. If the one swearing committed polytheism in the wording of his oath and nothing else, then this would be minor polytheism. However, this would be major polytheism if the one swearing intended to glorify a created being in the same way he glorifies Allah, like many of the Sufis who swear by their Awliyaa (pious slaves) and Shaykhs, whether they are dead or alive. They glorify them in their hearts to the extent that they would never swear by them falsely, although they might swear by Allah falsely. This represents major polytheism which takes one outside the fold of Islam, because the things by which they swear are more exalted, glorified and feared in their sight than Allah the Almighty.

التعريف اللغوي المختصر :

"Yameen": oath-taking, swearing. It was called as such because people used to strike the "yameen" (right hand) of one another upon entering into alliance. Other meanings: the hand, blessing, strength.