The time or activity where a teacher teaches students at school or academy
When to use
Learning time at school, Academy lecture, Online class
The nuance
수업 refers to official education time or lectures where direct teaching occurs.
수업 (su-eop, sueop) · 숙제 (suk-je, sukje) · 시험 (si-heom, siheom)
수업 is the learning time, 숙제 is the study done at home, and 시험 is the chance to evaluate skills.

One lane per word — no nested boxes, just the gist.
The time or activity where a teacher teaches students at school or academy
When to use
Learning time at school, Academy lecture, Online class
The nuance
수업 refers to official education time or lectures where direct teaching occurs.
Homework or assignments students must do at home after class
When to use
Studying at home, Assignment submission, Solving teacher-given problems
The nuance
숙제 means assignments or study students must complete at home after class.
An evaluation or test taken to assess a student's learning achievement
When to use
Midterm exam, Final exam, Certification test
The nuance
시험 means an official test or examination to assess knowledge or ability.
오늘 수업이 3시에 시작해요.
o-neul su-eop-i 3si-e si-jak-hae-yo., o neul su eop i 3si e si jak hae yo.
Correct when talking about class time.
오늘 숙제가 3시에 시작해요.
o-neul suk-je-ga 3si-e si-jak-hae-yo., o neul suk je ga 3si e si jak hae yo.
Homework is not something that 'starts' at a time; this usage is incorrect.
수업 후에 숙제를 해야 해요.
su-eop hu-e suk-je-reul hae-ya hae-yo., su eop hu e suk je reul hae ya hae yo.
Natural sentence indicating homework done after class.
시험 후에 숙제를 해요.
si-heom hu-e suk-je-reul hae-yo., si heom hu e suk je reul hae yo.
It's uncommon to say you do homework after an exam; they are separate activities.
이번 시험은 어려웠어요.
i-beon si-heom-eun eo-ryeo-woss-eo-yo., i beon si heom eun eo ryeo woss eo yo.
Appropriate expression when evaluating an exam.
이번 수업은 어려웠어요.
i-beon su-eop-eun eo-ryeo-woss-eo-yo., i beon su eop eun eo ryeo woss eo yo.
Correct when talking about the difficulty of a class.
숙제는 학교에서 해요.
suk-je-neun hak-gyo-e-seo hae-yo., suk je neun hak gyo e seo hae yo.
Homework is usually done at home, so saying it is done at school is incorrect.
시험 준비를 위해 숙제를 열심히 했어요.
si-heom jun-bi-reul wi-hae suk-je-reul yeol-sim-hi haess-eo-yo., si heom jun bi reul wi hae suk je reul yeol sim hi haess eo yo.
Correctly expresses doing homework as part of exam preparation.
Which sentence corresponds to '수업'?
Which sentence uses '숙제' correctly?
Which sentence is correct about '시험'?
What does it mean?