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NAI-form verbs (Lesson 21)Verbs that end with NAI are called NAI-form verbs. Let me explain how you can turn MASU-form verbs into NAI-form verbs. That is to change the MASU-form into the casual negative NAI-form. First, if the vowel in the syllable just before MASU ends with "E", all you have to do is to change MASU to NAI. For example, TABEMASU (to eat) becomes TABENAI (not to eat).
Next, if the vowel in the syllable just before MASU ends with "I", there are two patterns. In the first pattern, you change MASU to NAI. For example, OKIMASU (to get up) becomes OKINAI (not to get up). In the second pattern, you drop MASU, then change the vowel in the syllable just before MASU to "A", and add NAI. Let me explain this with IKIMASU (to go) as an example. Here, the syllable before MASU is KI. You first change KI to KA, and add NAI. So, the NAI form of IKIMASU is IKANAI (not to go).
But after you drop MASU, if the syllable just before MASU is the vowel "I" and it is not attached to a consonant, you change "I" to WA, and add NAI. So, TSUKAIMASU (to use) becomes TSUKAWANAI (not to use).
Finally, let me introduce a verb which conjugates irregularly. KIMASU (to come) becomes KONAI (not to come).
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