Yōga Sūtra 2.05

अनित्याशुचिदुःखानात्मसु नित्यशुचिसुखात्मख्यातिरविद्या।

Ignorance (avidya) understands that which is not permanent as permanent, that which is unclean as clean, that which is misery as pleasure, that which is not self as self.

A definition of no-knowledge or ignorance is given. So knowledge is the ability to discriminate permanent from non-permanent, benevolent from sorrow, clean from unclean and self from not-self. E.g: material procession is temporary, not smoking is benevolent while being addicted to smoking is sorrow, stale food like wine is unclean compared to freshly prepared food, physical body is not self, etc.