क्षर-अक्षर

Kṣara (क्षर) is what perishes, and akṣara (अक्षर) is what does not. In chapter 15 the Lord says that there are two kinds of beings in this world, the perishable and the imperishable. All bodies of creatures are perishable, and what stays unchanged is called imperishable (Gita 15.16).

The word "imperishable" appears in chapter 12 too, in another passage. There Arjuna asks about those who worship the imperishable unmanifest, and the Lord describes it: imperishable, beyond words, unmanifest, all-pervading, beyond thought, unchanging and unmoving (Gita 12.3).

Common misreading: taking the perishable to be bad, and the imperishable to be the Lord Himself.

Better sense: in chapter 15 beyond both the perishable and the imperishable stands the Supreme Person, called the Supreme Self (Gita 15.17). The Lord says He is beyond the perishable and higher than the imperishable (Gita 15.18). So the word does not carry one fixed sense everywhere. It is read by its passage.

The comparison of devotion with worship of the unmanifest is in Devotion or the Unmanifest.