Ijtihad (Arabic: اجتهاد‎‎ ijtihād, lit. effort, physical or mental, expended in a particular activity)[1] is an Islamic legal term referring to independent reasoning[2] or the thorough exertion of a jurist's mental faculty in finding a solution to a legal question.[1] It is contrasted with taqlid (imitation, conformity to legal precedent).[2][3] According to classical Sunni theory, ijtihad requires expertise in the Arabic language, theology, revealed texts, and principles of jurisprudence (usul al-fiqh),[2] and is not employed where authentic and authoritative texts (Qur'an and Hadith) are considered unambiguous with regard to the question, or where there is an existing scholarly consensus (ijma).[1] Ijtihad is considered to be a religious duty for those qualified to perform it.[2] An Islamic scholar who is qualified to perform ijtihad is called a mujtahid.[1]
https://en.wikipedia.org/wiki/Ijtihad