"Ijmā‘": the agreement among a group of people over a certain matter.
"Ittifāq": agreement, conformity and closeness between two things. Other meanings: convergence, unity, harmony.
Sources of Islamic legislation whose validity are not debated by the scholars of the Muslim Ummah. They are the Qur’an, the Sunnah, "ijmā‘" (consensus), and "qiyās" (analogy).
Not doing something despite of being able to do it, whether it be intentionally or unintentionally.