1.
what, what matter, what on earth
Used to ask or express surprise about what is happening. More formal or dramatic than simply なに.
何事かと思った。
I wondered what was going on.
外で大きな音がして、何事かと窓を開けた。
There was a loud noise outside, so I opened the window to see what was happening.
何事もなかったように振る舞った。
He acted as if nothing had happened.
2.
everything, anything, all matters
Used with も to mean 'everything' or 'anything,' often in the context of approaching all things with a certain attitude.
何事も経験だ。
Everything is an experience.
何事も最初が肝心だ。
In everything, the beginning is crucial.
何事にも全力で取り組む姿勢が大切だ。
The attitude of giving your all in everything is important.
COMMON PATTERNS:
- 何事かと思う (to wonder what is happening)
- 何事もなかったように (as if nothing had happened)
- 何事も~だ (everything is ~)
- 何事にも (in everything, for anything)
REGISTER: More formal and literary than なに. Carries a sense of gravity or importance. 何事もなかったように is an extremely common set phrase.