FARD (plural: fara’id)
A duty made compulsory on all Muslims by the command of Allah in the Holy Qur’an.
WAJIB (plural: wajibat)
A duty made compulsory on all Muslims by the command of the Holy Prophet Muhammad [s] in the Hadith.
SUNNAH (plural: sunan)
An act or regular habit performed by the Holy Prophet Muhammad [s]. A Muslim is expected to emulate the blessed Prophet [s] in all his deeds and habits. There is great reward in performing any Sunnah action.
MUSTAHAB (plural: mustahabbat) or NAFL (plural: nawafil)
A voluntary or desirable act or deed. These were performed only occasionally by the Holy Prophet [s]. If anyone performs a Mustahab or Nafl act he will be rewarded, however, if he neglects it, there will be no sin.
MAKRUH (plural: makruhat)
An undesirable or disliked act or thing. Makruhat should be avoided, although they are not altogether forbidden.
A permissible act or thing.
NAQID (plural: nawaqid)
An act or thing which nullifies a deed. For example eating while fasting would be a naqid of the fast (sawm), nullifying it, and requiring that it be repeated.