Masu Form and its Conjugations

In this lesson you'll learn how to conjugate dictionary form verbs into masu form, the polite form, and how to conjugate masu form verbs for tense, negation, and volition.

Recommended background:

From Dictionary Form to Masu Form

The nice thing about formal Japanese is that the main verb of a sentence invariably appears in masu form, the polite form. Masu form itself is affirmative (positive) and present tense, just like dictionary form, so there's one additional step if you need past tense or negation. Along with the real masu form, these derived forms are also collectively referred to as "masu form".

The good news is that once you get a verb from dictionary form into (literal) masu form, any further conjugation is identical for all verbs since they now all have the same ending, so most of the challenge is in the first step.

I'll give you both the linguistic derivation, which explains what's really going on underneath the surface, and the quick rule for conjugating.

(You can skip to the quick version if you're not interested in the details at the moment.)

The Full Derivation

Remember from Japanese Verbs and Conjugation that Japanese verbs are made up of three parts:

  1. A verb stem, which is in one of two conjugation classes
  2. Zero or more auxiliary verbs, each of which is also in one of the same two classes
  3. A present or past tense suffix

A dictionary form verb has just the verb stem and the present tense suffix, so we need to take off the tense suffix and add the auxiliary, then bring back the tense.

For Group I verbs, the tense suffix is -u, and for Group II, it's -ru. So using our knowledge of which verbs are in which group, we can get the verb stem. For some Group I verbs, we also have to change the final consonant in the stem to its underlying form.

  Dict. Form Components Stem
Group I matsu mat-u mat-
Group II kariru kari-ru kari-

Remember from Hiragana and the Japanese Sound System that the 'ts' in the mora 'tsu' and the 'ch' in the mora 'chi' are really each a 't' deep down (that's why they're in the same Hiragana column), and it's the vowel that follows that causes the pronunciation to change, yielding a different surface form. Since we want remove the vowel, the 'ts' needs to go back to being a 't'.

Next, we add the auxiliary. In this case, the real auxiliary isn't -masu, but -imas-. The 'i' in -imas- causes a sound change in some Group I verbs and all Group II verbs: in Group I, it may cause the final consonant in the stem to change, and in Group II, the 'i' itself deletes because it follows a vowel.

Group I mat + imas -> mach-imas-
Group II kari + imas -> kari-mas-

Finally, we add the present tense suffix, -ru. Imas is a Group I verb, so the 'r' gets deleted, and the result is just -u. In summary:

  Matsu (Group I) Kariru (Group II)
Underlying Form mat-imas-ru kari-imas-ru
Changes 't' -> 'ch'
'r' in -ru deleted
'i' in -imas- deleted
'r' in -ru deleted
Surface Form mach-imas-u kari-mas-u

In practice, you're not going to go through this entire process every time you want to conjugate a verb. The point of going through the long derivation like this is to help you understand that there are patterns behind the seemingly arbitrary rules, and to give you a fallback in case you forget the rules.

The Quick Rules

This time, we'll use the Hiragana chart as a guide to the conjugation pattern, at least for Group I. Here's the idea: every Group I verb in dictionary form ends in a u-dan Kana: u, ku, gu, su, tsu, nu, bu, mu, or ru, while in masu form, the final mora before masu is an i-dan Kana. So the rule is to change the u-dan Kana to the corresponding i-dan Kana and add -masu.

Group II verbs are even easier. Every Group II verb in dictionary form ends in -ru, and the masu form has the same stem with -masu attached instead. So all you have to do is remove -ru and add -masu.

Dictionary Form to Masu Form
  Rule Example Romaji
Group I Change the final u-dan Kana to an i-dan Kana
in the same column and add -masu.
さす -> さします sasu -> sashimasu
Group II Remove -ru and add -masu. みる -> みます miru -> mimasu

The one impure thing about this approach is that it makes it sound like the 'i' is part of the stem in Group I verbs, which simply isn't true. But for all practical purposes, this is the easiest way to get the job done.

Irregular Verbs

The irregular verbs suru (to do) and kuru (to come) are conjugated as follows:

Hiragana Romaji
する -> します suru -> shimasu
くる -> きます kuru -> kimasu

You'll use these two verbs constantly, so memorizing their special conjugations shouldn't take too much effort.

Conjugations of Masu Form

Now we'll look at the other "masu" forms, which have endings other than the non-past (present) tense suffix.

Conjugations of Masu Form
  Hiragana Romaji
Non-past -ます -masu
Past -ました -mashita
Non-past -ません -masen
Past -ませんでした -masen deshita
Volitional -ましょう -mashou

Masu itself is the primary irregular auxiliary in Japanese – while masu has the same simple past and non-past forms as any main verb with a stem ending in 's', the other forms are unique.

We haven't talked about past tense much yet, and I'm going to put off that discussion one more time – there are a couple interesting things going on here that are more appropriate for a lesson on usage. For now, I'll just tell you that event verbs (e.g. not state verbs) behave mostly like English event verbs, so for those verbs you can safely use past tense as in English. Non-past tense, as I've mentioned before, can be present or future tense depending on context.

Negative form, –masen, presents no particular difficulties. If you already know how to use de wa arimasen, then you're all set. The one weird thing about -masen is that unlike most verby things in Japanese, it does not accept the past tense marker -ta, so instead you have to add deshita, the past tense of desu. In this case, deshita is bleached of its meanings of "to be" and politeness.

The volitional form, –mashou, doesn't have an direct English counterpart, but has the basic meaning of expressing the speakers wishes or intention. Most of the time, it simply means "let's". So ikimasu is "(I will) go" and ikimashou is "let's go".

An that's it! As we've discussed a couple of times, Japanese verbs do not agree with their subjects, so there are no additional forms to learn.

In the following lessons, we'll hold off on learning any additional form conjugations for a bit and focus on the particles and other tidbits that will allow you to make the maximum use of what you already know.

What Next?

Beginning Vocabulary: Verbs

Comming soon:

  • Talking About Hobbies
  • Talking About Languages and Countries
  • Particles for Location and Direction: De, Ni, E

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