The concepts are; 'shin' (the most strictly formal), gyo (the middle of 'shin' and 'so'), 'so' (the most casual), and these three kinds are divided into further three categories respectively, according to the degree of formalities, 'shin,' 'gyo', 'so.'
真の（さらに真、行、草）、行の（さらに真、行、草）、草の（さらに行、草）などだ。