가끔(ga-kkeum, gakkeum)
An adverb used for events that happen occasionally but with some regularity
When to use
Everyday frequency, Regular intermittent events, Meeting friends, Hobby activities
The nuance
Used to express events that occur occasionally with some regularity in both everyday and formal contexts.
드물게(deu-mul-ge, deumulge)
An adverb expressing very rare or seldom occurrences
When to use
Rare events, Exceptional situations, Scientific reports, Descriptions of natural phenomena
The nuance
Used to emphasize situations that are hard to occur or almost non-existent, often found in formal documents or news reports.