잃다(il-da, ilda)
To lose something, either tangible or intangible, typically focusing on the fact of loss.
When to use
losing opportunity, losing money, losing memory
The nuance
Used mainly for abstract or result-focused loss, regardless of whether recovery is possible.
잃어버리다(il-eo-beo-ri-da, ileobeorida)
Emphasizes temporarily misplacing something or someone, implying the possibility of recovery.
When to use
losing keys, getting lost, misplacing phone
The nuance
Used for concrete loss of objects or people, with an intention or hope to find again.