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natural; reasonable; obvious
usual; common; ordinary; commonplace; the norm
それは当たり前のことだよね。
That's a natural thing.
当たり前のことを当たり前にやる。
Do the obvious things as a matter of course.
毎日ご飯が食べられるのは当たり前のことではないと思う。
I don't think being able to eat every day should be taken for granted.