1.
reason, logic, principle
The underlying logic or natural principle that makes something the way it is.
道理に合わない。
It doesn't make sense.
子どもでも分かる道理だ。
It's a principle even a child can understand.
道理をわきまえた人だ。
They're a person who understands reason.
2.
no wonder, that explains it
Used as an adverb (道理で) to express that something now makes sense in light of new information.
道理で寒いわけだ。
No wonder it's cold.
道理で連絡がないと思ったら、入院していたのか。
No wonder I hadn't heard from them — they were in the hospital.
引っ越したのか。道理で最近見かけないわけだ。
So they moved. No wonder I haven't seen them around lately.
道理 has two main uses: as a noun meaning "reason" or "logic," and as part of the adverbial expression 道理で meaning "no wonder."
COMMON PATTERNS:
- 道理に合う: to make sense, to be reasonable
- 道理に合わない: to be unreasonable, illogical
- 道理で〜わけだ: no wonder ~
- 道理をわきまえる: to understand reason
USAGE: The expression 道理で〜わけだ is very common in everyday conversation. It conveys a moment of realization — something that was puzzling now makes sense.