Khaas: A word that refers to a specific meaning or object without referring to anything else. E.g. “Zayd” refers to a specific individual; “Man” refers to a specific gender.
– Practised upon completely
– Khabar Wahid or Qiyaas cannot change the ruling of Khaas
وَٱلۡمُطَلَّقَـٰتُ يَتَرَبَّصۡنَ بِأَنفُسِهِنَّ ثَلَـٰثَةَ قُرُوٓءٍ۬ۚ (2:228)
ثَلَـٰثَةَ is Khaas because it is a specific number, hence must be acted upon completely.
‘Aam: A word that refers to a number of individuals or items of a group at the same time.
1) Ghayr Makhsoos al-Ba’d (i.e. no exclusions from it): same ruling as Khaas; practised upon completely.
فَٱقۡرَءُواْ مَا تَيَسَّرَ مِنَ ٱلۡقُرۡءَانِ (73:20)
مَا is ‘Aam and, here, includes the entire Qur’an, i.e., whichever part of the entire Qur’an can be easily recited.
2) Makhsoos al-Ba’d (i.e. some exclusions from it): Wajib to practise on what hasn’t been excluded; probability of further exclusion; permissible to exclude with Khabar Wahid & Qiyas as long as 3 items/members left.
“There is general agreement to the effect that the Khass is definitive (qat’i) in its import, but the ulema have differed as to whether the ‘Amm is definitive or speculative (zanni). According to the Hanafis, the application of ‘Amm to all that it includes is definitive, the reason being that the language of the law is usually general and if its application were to be confined to only a few of the cases covered by its words without a particular reason or authority to warrant such limited application, the intention of the Lawgiver would be frustrated.[49. Shatibi, Muwafaqat, III, 153; Abu Zahrah, Usul, p.124; Abdur Rahim, Jurisprudence, p. 82.] The majority of ulema, including the Shafi’is, Malikis and Hanbalis, maintain on the other hand that the application of ‘Amm to all that it includes is speculative as it is open to limitation and ta’wil, and so long as there is such a possibility, it is not definitive. The result of this disagreement becomes obvious in the event of a conflict between the ‘Amm of the Qur’an and the Khass of the Hadith, especially the weak or the solitary Hadith. According to the majority view, a solitary Hadith may specify a general provision of the Qur’an, for the ‘Amm of Qur’an is zanni and the Khass of a solitary Hadith, although definitive in meaning, is of speculative authenticity. A zanni may be specified by a qat’i or another zanni.[50. Abu Zahrah, Usul, p.125; Badran, Usul, p.381.] To the Hanafis, however, the ‘Amm of Qur’an is definite, and the solitary Hadith, or qiyas for that matter, is speculative. A definitive may not be limited nor specified by a speculative.” [Kamali, Principles of Islamic Jurisprudence, pg.105]