거의(geo-ui, geoui)
In negative sentences, '거의 ~않다' means 'mostly not' or 'almost not', allowing for some exceptions.
When to use
Partial negation, Almost complete, Frequency expression
The nuance
'거의' is used in negative sentences to express 'almost not' or 'mostly not', not a total negation.
전혀(jeon-hyeo, jeonhyeo)
In negative sentences, '전혀 ~않다' expresses complete negation, meaning 'not at all'.
When to use
Complete negation, Strong negation emphasis, Negation emphasis
The nuance
'전혀' is used in negative sentences to indicate total negation without exception.