Samādhi: 'concentration' 'tranquility' lit. 'the mental state of being firmly fixed' sam+ā+Ö hā is the fixing of the mind on a single object.,One-pointedness of mind cittass ekaggatā Brother Visakha, this is called concentration; M. 44. Concentration - though often very weak - is one of the 7 mental properties inseparably associated with all consciousness. Cf.nāma, cetanā.
Right concentration sammā-samādhi as the last link of the 8-fold path see: magga is defined as the 4 meditative absorptions jhāna. In a wider sense, comprising also much weaker states of concentration, it is associated with all kammically advantageous kusala consciousness. Wrong concentration micchā-samādhi is concentration associated with all kammically disadvantageous akusala consciousness. Wherever in the texts this term is not differentiated by 'right' or 'wrong', there 'right' concentration is meant.
In concentration one distinguishes 3 grades of intensity:
1 'Preparatory concentration' parikamma-samādhi existing at the beginning of the mental exercise.
2 'Neighbourhood concentration' upacāra-samādhi i.e. concentration 'approaching' but not yet attaining the 1st absorption jhāna, which in certain mental exercises is marked by the appearance of the so-called 'counter-image' patibhāga-nimitta.
3 'Attainment concentration' appanā-samādhi i.e. that concentration which is present during the absorptions.
Concentration connected with the 4 noble path-moments magga and fruition-moments phala is called supra-mundane lokuttara having Nibbāna as object. Any other concentration, even that of the most sublime absorptions is merely mundane lokiya.
According to D. 33, the development of concentration samādhi-bhāvanā may procure a 4-fold blessing: 1 present happiness through the 4 absorptions; 2 knowledge and vision ñāna-dassana - here probably identical with the 'divine eye' see: abhiññā through perception of light kasina 3 awareness or mindfulness and clear comprehension through the clear knowledge of the arising, persisting and vanishing of feelings, perceptions and thoughts; 4 ceasing of all fermentations āsavakkhaya through understanding the arising and passing away of the 5 groups forming the objects of clinging see: khandha
Concentration is one of the 7 factors of enlightenment bojjhanga, one of the 5 spiritual abilities and powers see: bala and the last link of the 8-fold path. In the 3-fold division of the 8-fold path morality, concentration and understanding, it is a collective name for the three last links of the path see: sikkhā.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.