have toとは

発音

• (英国発音) IPA^(key): /ˈhæv.tuː/ (careful)
• (米国発音) IPA^(key): /ˈhæf.tu/ (careful)
• (英国発音, 米国発音) IPA^(key): /ˈhæf.tə/ (relaxed pronunciation)

動詞

have to (三人称単数 現在形 has to, 現在分詞 having to, 過去形および過去分詞形 had to)

1. Must; need to; to be required to. Indicates obligation.
   • 1898, Winston Churchill, chapter 1, in The Celebrity:

     I was about to say that I had known the Celebrity from the time he wore kilts. But I see I will have to amend that, because he was not a celebrity then, nor, indeed, did he achieve fame until some time after I left New York for the West.

   • 2013 July-August, Henry Petroski, “Geothermal Energy”, in American Scientist, volume 101, number 4:

     Energy has seldom been found where we need it when we want it. Ancient nomads, wishing to ward off the evening chill and enjoy a meal around a campfire, had to collect wood and then spend time and effort coaxing the heat of friction out from between sticks to kindle a flame.

   I just have to have that shirt;  you have to wear a seat belt

2. (with be) Must (logical conclusion).

   that has to be the postman;  it has to be an electrical fault

使用する際の注意点

have to is always followed by a bare infinitive verb, unless the verb is assumed:

I don't want to go to school, but I have to.

同意語

("obligation"):

• gotta
• got to, have got to

("logical conclusion"):

• be bound to
• gotta
• got to, have got to

参考

• Appendix:English modal verbs
• Appendix:English tag questions