A subset of a poset (or proset) which is a directed set (when regarded as a poset in its own right) is a directed subset, and dually.
आदेश–निर्देशन तब मात्र शीघ्र प्रवाह हुन सक्छ, जब प्रहरीमा दर्जागत तह थोरै हुन्छ ।