Japanese verbs are divided into two broad forms, which are the polite form and the plain form. The polite form of verbs is used frequently in formal conversations. The plain for of verbs is used while talking with friends and family. In other words, it is used for communicating in informal situations. This form consists of verbs of all the three groups. The dictionary form, te form, ta form, nai form and nai de form are all different type of forms of verbs which come under the plain form of Japanese verbs.
Te form of Japanese Verb:
While changing a verb into "te form" there is different rules for different groups. The verbs in this form end either in "te" or in "de". We always need to consider the dictionary form of a verb while changing it into the "te form". In case of group 1
In case of group 2 the only rule to follow for all the verbs included in this group is, remove "ru" from the root verb form and add "te" at the end. E.g. miru (To see) mite
In case of Group 3 as there are only two verbs, their form is as follows:
It is very important to learn the rules for group 1. Comparatively rule for group 2 is very easy and group 3 is the easiest.
Ta Form of Japanese verb:
Once you are clear with how to change a verb into "te" form then it is very easy to change the verbs into "ta" form. "Ta" form is the past tense of Japanese verbs in plain form. The rule for group 1 verbs is, first change the verb into "te" form. Next step will be just replacing the end "te" to "ta" and in case of "de" replacing it by "da". E.g.
kau (to buy) katte katta Oyogu (To swim) oyoide Oyoida
In case of group 2 just remove "te" and add "ta". In other words, add "ta" at the end of the masu base form of the verbs of this group. E.g. tabe (to eat) tabeta
In case of group 3, "shite" becomes "shita" and in the same way, "kite" become "kita" Nai Form of Japanese verb:
A Japanese verb when used in the "nai form" indicates some negative meaning of the sentence. This form also has different rules for each group. Again, here also we have to first consider the dictionary form of verbs irrespective of the group to which they belong. Lets see each group one by one.
In group1, first convert the verb into its dictionary form. All the "u" sound consonants should be removed and all the "a" sound should be added. This means that ku, su, tsu, nu, hu, mu, ru, gu, zu, bu and pu will be replaced by ka, sa, ta, na, ha, ma, ra, ga, za, ba and pa respectively. There is only one exception for "u" ending root verb. The verbs having root verbs ending with "u" will be replaced by "wa" and not "a". The last step would be to add "nai" to all the "a" ending verbs. E.g. kau (To buy) kawa kawanai Wakaru (To understand) wakara- Wakaranai
In group2, directly add nai to the stem form of the verb. This applies to all the verbs, which come under group 2. E.g. Akeru (To open) ake akenai
The "nai form" of the two verbs of group 3 is "shinai" and "konai". As the verbs of this group do not follow any rules, they have to be learnt as given.
Following are the tables that have the Japanese verbs and their different forms according to their groups.