while vs during の絶対区別 (3級超頻出ひっかけ)
while=接続詞 (後ろに S+V の節): ○ "while I was eating"
during=前置詞 (後ろに名詞): ○ "during dinner" — 後ろが節か名詞かで使い分け。
while + 進行形 (典型構文)
"While I was studying, the phone rang." (主節は過去形)
"While she is sleeping, please be quiet." (現在形) — 同時進行を強調。対比の while = whereas (やや堅い)
"While [Whereas] Japan has 4 seasons, Hawaii has only 2." 3級長文の対比表現で頻出。for a while = しばらくの間 ("wait for a while") は名詞用法。