걱정하다(geok-jeong-ha-da, geokjeonghada)
To be concerned or worried about a specific problem or situation
When to use
exam results, health issues, delayed appointment
The nuance
Use 걱정하다 when thinking about a clear, specific cause or situation; it implies conscious concern over identifiable issues.
불안하다(bul-an-ha-da, bulanhada)
To feel vague, persistent unease or anxiety, often without a specific cause
When to use
vague fear of future, pre-exam nervousness, uncertain situations
The nuance
Use 불안하다 to express a vague, uneasy feeling often without a clear cause; suitable for prolonged or mental/emotional states.