'Aqd literally means tying tightly, as tying a rope. 'Aqd carries the meanings of covenant and fulfillment, as we read in the Quran surah Al Maidah verse 1:

O ye who believe! Fulfill (all) obligations. Lawful unto you (for food) are all four-footed animals, with the exceptions named: but animals of the chase are forbidden while ye are in the Sacred Precincts or in pilgrim grab: for Allah doth command according to His Will and Plan.

The plural of word 'uqud above is mentioned in commanding the faithful to keep their covenants. God the Most High also commands the faithful to keep their promises and covenants in Al Quran surah Al Isra' verse 34:

Come not nigh to the orphan's property except to improve it, until he attains the age of full strength; and fulfill (every) engagement, for (every) engagement, will be enquired into (on the Day of Reckoning).

In another verse of Quran (An Nahl verse 91), we read Allah's command to the faithful to keep the obligations, which He had imposed on them when they embraced belief:

Fulfill the Covenant of Allah when ye have entered into it, and break not your oaths after ye have confirmed them: indeed ye have made Allah your surety; for Allah knoweth all that ye do.

In Hadith ibn 'Abbas, commenting on a Quranic verse, we read that 'aqd means covenant, agreement and faith. In Arabic usage, we read that a man cannot tie ('aqd) a rope to mean he is too poor and feeble to do anything.

Contract also means an engagement and agreement between two persons in a legally accepted, impactful and binding manner such a proposal made by one parties and accepted by other party in a way which has an impact on the subject matter of the contract.

Husein al Nuri defined in Al Iltizam page 29, as the expression of exchange between two confirming wills in an aim to have a legal impact of a financial nature, be it origination, modifying, transferring or ending a commitment. Contract in man-made laws is an agreement between two wills producing a legal impact. The act of selling is a contract between the seller and the purchaser in which the seller takes it upon himself to transfer to the buyer the ownership of something or some other financial right in return for a monetary price (agreement of two or more wills to initiate, transfer, modify or end a commitment). According to Egyptian civil law (article 418) this transfer can include ownership as well as any other financial right. The important thing is that there should be a legal impact ensuing from the contract transaction. Inviting a friend to a meal, giving him help or promising him a reward are convention and not contract, as they do not have a legal effect.