Khas is a word assigned to a defined or limited meaning. The source shows three forms:
• Individual: one named person, such as زَيْدٌ (Zayd).
• Kind: one kind within a wider class, such as رَجُلٌ (a man) or فَرَسٌ (a horse).
• Genus or broad class: a wider class, such as إِنْسَانٌ (human) or حَيَوَانٌ (animal).
The key is a defined or limited assignment; Khas does not always mean only one physical object.