妙法蓮華經玄義 6.90

6.90

差別者，脩多羅有九種。經云：從如是至奉行，一切名脩多羅。是則脩多羅名通而體總，皆名為經，故名通。就文字經體分為十二部，故體總也。

Regarding 'distinctions', sūtras are of nine kinds. A scripture says: 'From "Thus [have I heard]" to "upheld and practiced," all is named sūtra.' Thus, the name of sūtra is general while its substance is comprehensive: because all are named scriptures, the name is general; because it is divided into the twelve divisions according to the written scriptural substance, the substance is comprehensive.