プログレッシブ和英中辞典(第4版)の解説
しょにち【初日】
❶〔開幕の日〕the first [opening] day [night]
初日を欠かさず見にいく人
〔芝居で〕a first-nighter
博覧会の初日はいつですか
When does the exposition open [start]?
❷〔相撲で，初白星〕
初日を出す
have one's first winning match (in a sumo tournament)
まだ初日が出ない
He still hasn't won a match in this tournament.
はつひ【初日】
the sunrise on New Year's Day
初日（の出）を拝みに行った
I went to watch [greet] the first sunrise of the year.