Tatridaṃ vissajjanaṃ. Ko samādhīti samādhi bahuvidho nānappakārako. Taṃ sabbaṃ vibhāvayituṃ ārabbhamānaṃ vissajjanaṃ adhippetañceva atthaṃ na sādheyya, uttari ca vikkhepāya saṃvatteyya, tasmā idhādhippetameva sandhāya vadāma, kusalacittekaggatā samādhi.
Ñ(III,2): Here are the answers :
(i) WHAT IS CONCENTRATION? Concentration is of many sorts and has various aspects. An answer that attempted to cover it all would accomplish neither its intention nor its purpose and would, besides, lead to distraction; so we shall confine ourselves to the kind intended here, calling concentration profitable unification of mind.