have to do, must, should, ought to
Verb negative stem +
This grammar point expresses a strong sense of duty, obligation, or necessity. It is a more formal and literary version of the common なければならない construction. It is often used in writing, formal speeches, or when stating rules and principles.
General Verbs
For most verbs, change the final vowel of the dictionary form to the 'a' sound and add
事務所へ行か
I must go to the office.
この本を読ま
I have to read this book.
Suru Verbs
The verb する (to do) and compound verbs ending in する change to せ before adding
毎日勉強せ
I must study every day.
もっと練習せ
I have to practice more.
The negative stem is the form used before adding ない (e.g., for 書く, the stem is 書か). A major exception is the verb する (to do), which becomes せ