妙法蓮華經玄義 2.81

2.81

說法妙者，謂說十二部法、小部法、大部法、逗緣法、所詮法、圓妙法，如理圓說，咸令眾生開、示、悟、入佛之知見，故言說法妙。

The subtlety of expounding the Dharma: this refers to expounding the twelve divisions of Dharma, the small division of Dharma, the great division of Dharma, the Dharma suited to capacities, the Dharma expressed, and the perfect and subtle Dharma. Expounding perfectly in accord with the principle, all causing sentient beings to open, show, awaken to, and enter into the Buddha's knowledge and vision; hence it is called the subtlety of expounding the Dharma.