The following is a translation from the Usul Al-Fiqh masterpiece of the Arabic book “The Islamic Personality Volume 3” by Sheikh Taqiuddin an-Nabhani. Please refer to the original Arabic for accurate meanings.
The address of legal responsibility [taklīf] is the address of the legislator related to compulsion or choice, that is, it is related to the request to perform an action or to abstain from an action, or to the option of choosing between performance and abstention.
If the address is related to a decisive request to perform an action, that action is wājib [obligatory] or fard, the two being synonymous. The wājib action is that which if not performed with an unqualified intention renders the person leaving it legally blameworthy. The meaning of the leaver being legally blameworthy is that the Book of Allah, the Sunnah of His Messenger (saw) or the Ijma’ al-Sahabah indicate that if a person leaves such an action he has acted deficiently and is blameworthy. There is no consideration given to the blame of the people on the omission of an action. Rather what is considered is the blame of the revelation. Further, there is no difference, from the perspective of obligation, between the action which is individually obligatory [wajib al-‘ayn] and the obligation of sufficiency [wajib ‘ala al-kifāyah].
If the address of the legislator is related to a non-decisive request to perform an action then that action is mandūb [recommended]. In the ritual worships [‘ibādāt] the word ‘sunnah’ is also synonymously used. The mandūb action is that which the performance of is legally praiseworthy, whilst its non-performance is not legally blameworthy. It is also referred to as nafilah [supererogatory].
If the address of the legislator is related to a decisive request to abstain from an action then that action is harām [prohibited] or mahdhūr, the two being synonymous. The harām action is that which the performance of is legally blameworthy. If the address of the legislator is related to a non-decisive request to abstain from an action then that action is makrūh [reprehensible]. The makrūh action is that which the abstention of is legally praiseworthy, whilst its performance is not legally blameworthy.
If the address of the legislator is related to the granting of an option to either perform an action or abstain therefrom then that action is mubāh [permissible]. This is in both the case that the option is given explicitly in the text or that it is understood from the text from the form [seegah] of the request, such as when a request to perform comes after a prohibition in the same matter but in two different contexts or situations, even if the request to perform comes in the imperative tense.
The legal rulings related to the address of legal responsibility are restricted to the above five (wājib, mandūb, mubah, makruh, harām)