#Glossary-**Admission**: Whether an item is allowed into cache at all.
-**Eviction**: Which resident item to remove when space is needed.
-**Recency**: How recently an item was accessed.
-**Frequency**: How often an item was accessed.
-**Scan pollution**: One-time accesses evicting genuinely hot items.
-**Ghost entries**: Metadata for recently evicted items to improve decisions.
-**Hot set**: The small subset of keys responsible for most accesses.
-**Hit rate**: Fraction of requests served by the cache.