used to

・"used to"は過去の習慣的行為や状態を表すのに使われる。
・一般動詞として扱われ、疑問文や否定文を作るには助動詞didを使う。

[正]He didn't use to smoke.
[正]He didn't used to smoke.
[誤]He used not to smoke.
[誤]He usen't to smoke.
[誤]He usedn't to smoke.
[正]Did he use to smoke?
[正]Did he used to smoke?
[誤]Used he to smoke?

・イギリス英語では助動詞としても扱われる。

[英]He didn't use to smoke.
[英]He didn't used to smoke.
[英]He used not to smoke.
[英]He usen't to smoke.
[英]He usedn't to smoke.
[英]Did he use to smoke?
[英]Did he used to smoke?
[英]Used he to smoke?

used toの関連項目