This is the 467th most frequent Korean word.
여야
"여야" in Korean means "ruling party and opposition party."
Here, '해야' stems from '여야', used to express necessity or obligation as part of a compound verb structure.
학생은 열심히 공부해야 합니다.
A student must study diligently.
'해야' here involves a compound structure indicating requirement before achieving an outcome.
축제에 참석하려면 티켓이 필요해야 해요.
You must need a ticket to attend the festival.
'여야' in '켜져 있어야' specifies a condition that must be met for the subsequent action to occur.