वृत्तयः पंचतय्यः क्लिष्टा अक्लिष्टाः ॥

vṛttayaḥ paṃcatayyaḥ kliṣṭā akliṣṭāḥ

There are five classes of modifications, (some) painful and (others) not painful.

In plain words: There are five kinds of thought-waves in the mind. Some cause pain and some do not.