Have got to 和 have to 為同義詞，意思是「必須，不得不」，其中 have got to 比較常用於口語以及非正式的情況或上下文中。我們在此使用 have (got) to (第三人稱則將 have 換成 has) 來指這兩個動詞。
Have got to 和 have to 的肯定形式
Have (got) to 位於主動詞之前。例如：
- I have got to finish this today. (我今天必須完成這件事)
- We have to go to Tokyo tomorrow on business. (我們明天得去東京出差)
Have (got) to 經常縮略，尤其是在口說時。例如：
- I’ve got to finish this today. (我今天必須完成這件事)
- We’ve to go to Tokyo tomorrow on business. (我們明天得去東京出差)
當主動詞及其受詞、補語等不言可喻時，have (got) to 可單獨存在 (以避免重複)。例如：
- John: Does Mary have to talk to her mother on the phone every week. (約翰：瑪麗每週都得跟她母親通電話嗎？)
Paul: Yes, she has (got) to. (保羅：沒錯，她必須這樣做)
Have got to 和 have to 的否定形式
Have to 的否定形式是用 do not、does not、did not 或 don’t、doesn’t、didn’t 來構成。例如：
- I don’t have to go to work by bus tomorrow. (我明天不必坐公車去上班)
Have got to 的否定形式是直接在 have 的後面加 not，不可使用 don’t、doesn’t、didn’t。例如：
- I haven’t got to go to work by bus tomorrow. (正)
- I don’t have got to go to work by bus tomorrow. (誤)
Have got to 和 have to 的疑問形式
Have to 的疑問形式是在主詞的前面使用 do、does、did 來構成。例如：
- Does Sam often have to go to the dentist? (山姆得經常去看牙醫嗎？)
- What time do we have to be there? (我們必須在什麼時間到那裡？)
Have got to 的疑問形式是直接將 have 挪到主詞的前面。例如：
- Has Cindy got to take flowers? (辛蒂必須帶花去嗎？)
- Why have you got to take these vitamin pills? (你為什麼要吃這些維他命藥丸？)
Have got to 和 have to 的含意
Have (got) to 是用來表示責任或義務 (obligations)，意為「必須，不得不」。雖然 have (got) to 在大多數情況下都可與 must 互換，但它們的含意卻有些不同。Have (got) to 是表示客觀上的需要，是別人加諸給我們的「必須」，而 must 是主觀上的必要，是自己認為的「必須」。試比較下列兩句：
- Sorry, I can’t come out now. I’ve got to tidy up my room before I’m allowed out. (對不起，我現在不能出去。我必須收拾好自己的房間才可外出)
- They said that they must work hard. (他們說他們必須努力工作)
說話時，若談到責任或義務，一般大多使用 have got to 而比較少用have to。
Have got to 和 have to 的時態
Have got to 只能用在現在式，而 have to 可用於任何時態。例如：
- I’ve got to study for my final exams. (我必須唸書準備期末考) (正)
I’d got to study for my final exams. (誤)
I’ll have got to study for my final exams. (誤) - I have to study for my final exams. (正)
I had to study for my final exams. (正)
I’ll have to study for my final exams. (正) - He has to change his plan. (他不得不改變計劃) (正)
He’d had to change his plan. (正)
He’ll have to change his plan. (正)
當未來的責任、義務或計畫已經確定時，一般通常使用 have (got) to 的現在式，而不使用未來式 will have to。例如：
- Helen’s got to go to the dentist by five o’clock. (海倫得在五點之前去看牙醫)
- I have to pick up my wife at the airport at seven o’clock. (我必須在七點去機場接我太太)