Epilanthanomai means to forget, to be forgetful, or to neglect. It can describe ordinary forgetting but often in the NT carries the weight of intentional or culpable neglect — the failure to keep something in mind that should be remembered. It appears in Hebrews in powerful exhortations: do not forget hospitality, do not forget God's faithfulness.
The most theologically profound use is Philippians 3:13 where Paul writes 'forgetting [epilanthanomai] what is behind and straining toward what is ahead' — here forgetting past failures and achievements alike is a spiritual discipline that enables forward momentum. The flip side appears in Hebrews 13:2: 'Do not forget [epilanthanomai] to show hospitality' — forgetting good obligations is a spiritual failure. But the most comforting use may be implicit: Isaiah 49:15 asks 'Can a mother forget her nursing child?' God's answer is He cannot — the divine memory never fails even when ours does.