There are three types of contracts under Islamic law: ṣaḥīḥ, fāsid and bāṭil. Contracts whose essence and attributes are lawful and which have no defects in their elements (aṣl) or characteristics (waṣf) are termed ṣaḥīḥ (valid). It should be stated that in respect of fāsid contracts only the waṣf may be defective, whereas in respect of bāṭil contracts the aṣl of the contract may also be defective. Fāsid is a type of contract permitted by its intrinsic characteristics but not its features. Its irregularity negates its validity, which if cured would make this type of contract valid. The concept of bāṭil relates to a contract whose elements and characteristics are devoid of legality. This difference between fāsid and bāṭil results in a difference of effects. Each of these contracts are divided into different types. Sometimes, the conditions incorporated in a contract also determine the nature of the contract as either valid, irregular, or void. This article discusses these contracts, as well as the requirements pertaining thereto, as well as the types of terms which are included in a contract and their effect on the validity of the contract.