Core Pattern Rule: Stating a Clear Reason with -기 때문에
The pattern -기 때문에 is used to express a clear, logical reason for a situation or action. It translates to "because" or "due to the fact that..." and places a stronger emphasis on the cause-and-effect relationship than other similar patterns.
Formation
It attaches directly to the stem of verbs and adjectives. For nouns, you use -(이)기 때문에.
Verb/Adjective Stem + -기 때문에
오다 (to come) → 오기 때문에 (because it's coming/raining)
비싸다 (to be expensive) → 비싸기 때문에 (because it's expensive)
Noun + -(이)기 때문에
학생 (student) → 학생이기 때문에 (because I am a student)
주말 (weekend) → 주말이기 때문에 (because it's the weekend)
Past Tense: Stem + -았/었기 때문에
늦다 (to be late) → 늦었기 때문에 (because I was late)
운동하다 (to exercise) → 운동했기 때문에 (because I exercised)
비가 오기 때문에 취소됐어요. / 학생이기 때문에 돈이 없어요. / 늦었기 때문에 못 들어가요.
Synonyms & Differences: -기 때문에 vs. -(아/어)서
While both patterns mean "because," they have important differences in nuance and grammar.
Nuance
-기 때문에: More objective and logical. It explicitly states the reason. It can sound slightly more formal or emphatic than -(아/어)서.
-(아/어)서: Implies a natural, sequential flow between the reason and the result. It's very common in everyday conversation and feels a bit softer.
Grammatical Restrictions
This is the most critical difference. Unlike -(아/어)서, the -기 때문에 pattern can be followed by commands, suggestions, and proposals.
Command:
위험하기 때문에 가지 마세요. (Correct)
위험해서 가지 마세요. (Incorrect - 위험하니까 would be used instead)
Statement:
비가 오기 때문에 길이 막혀요. (Correct - logical reason)
비가 와서 길이 막혀요. (Correct - natural flow, more common in speech)