일어나다(il-eo-na-da, ileonada)
Refers to physically getting up from lying down or a resting position.
When to use
Getting up after waking up in the morning, Standing up from a chair, Getting up after falling down
The nuance
Used in everyday, natural contexts; rarely used in formal or official situations.
기상하다(gi-sang-ha-da, gisanghada)
Specifically means officially getting up from bed in the morning, mainly used in formal contexts like military, school, or official events.
When to use
When a morning wake-up order is given in the military, Getting up at school wake-up time, Reporting getting up at an official event
The nuance
Primarily used in formal and official situations; unnatural in casual conversation.