Meaning of FORMULA in English
Set way of saying and doing something.
Formula of temporary marriage.
Useful information: Since it is a contract, mut'a requires a declaration and an acceptance. As in permanent marriage, the declaration is the prerequisite of the woman. It must consist of one of three Arabic formulas, the same three which are employed by the Shi'is in permanent marriage. Al-Sayyid al-Murtada  is said to have added that a slave girl may employ the formula 'I have allowed you' (abahtu-ka) or 'I have considered you lawful' (hallaltu-ka),  but his words have not been confirmed by others. Al-Shahid al Thani writes: 'To me it seems more correct to limit ourselves to the first three phrases.'  Apparently there is no disagreement on the point that the woman may not employ expressions like: 'I have given you possession', 'I have given to you as a gift', 'I have rented to you', 'I have lent to you', etc.
The 'acceptance' is made by the man after the woman has made her declaration. His words must demonstrate that he is satisfied with the declaration. For example, he may say: 'I will accept the marriage', or 'I accept the mut'a.' If he should say only: 'I accept' or 'I am satisfied', the contract is valid.
Advanced Islamic English dictionary. Расширенный исламский словарь английского языка. 2012