a matter of course; what is to be expected; par for the course
Used to state that something is natural, obvious, or to be expected under the circumstances. Often appears in explanatory or evaluative contexts.
It's only natural that he gets angry.
It's a matter of course that those who make an effort succeed.
Standard kanji-kana mixed spelling.
Variant with 事 instead of こと; slightly more formal or written style.
Phrase composed of 当然 (touzen, 'natural' or 'obvious') + の (possessive particle) + こと (koto, 'thing' or 'matter'). Literally 'a matter of naturalness'.