Japanese Desu Masu Form: Complete Guide to Polite Japanese

Understanding the Japanese Desu Masu Form: Your Guide to Polite Japanese

When you start to learn Japanese, one of the first things you'll encounter is the です・ます (desu/masu) form. This is basically the foundation of polite Japanese, and honestly, you'll use it constantly in everyday conversations. If you've ever heard Japanese people speaking and noticed those "desu" and "masu" sounds at the end of sentences, that's exactly what we're talking about here.

Here's the thing: Japanese has different politeness levels built right into the grammar. The desu/masu form sits right in the middle as the standard polite way of speaking. You'll use it with people you don't know well, at work, in stores, with teachers, and pretty much any situation where you want to sound respectful without being overly formal.

The good news? Once you understand how です and ます work, you've got a solid foundation for speaking Japanese in most everyday situations. The grammar follows predictable patterns, and with some practice, it becomes second nature.

What Exactly Is です (Desu)?

Let's start with です (desu). This little word functions as what linguists call a copula, which is basically a word that links a subject to a description or identity. Think of it like the verb "to be" in English.

You use です after nouns and adjectives to make your sentences polite. The basic pattern looks like this:

Subject wa Noun/Adjective desu

For example:

The particle wa (written as は but pronounced "wa") marks the topic of your sentence, and です comes at the very end to make everything polite. Without です, you'd have the casual form だ (da), which you'd use with close friends or family.

Conjugating です

The desu conjugation is pretty straightforward. Here are the main forms you need to know:

Present affirmative: です (desu) = is Present negative: じゃないです (ja nai desu) or じゃありません (ja arimasen) = is not Past affirmative: でした (deshita) = was Past negative: じゃなかったです (ja nakatta desu) or じゃありませんでした (ja arimasen deshita) = was not

Examples:

One thing that confuses beginners: when you use an i-adjective (like 暑い atsui = hot), you conjugate the adjective itself and then add です. The です here adds politeness but doesn't really change the grammatical meaning. So 暑いです (atsui desu) uses the adjective 暑い in its plain form plus です for politeness.

What About ます (Masu)?

Now for ます (masu). This one attaches to verbs to make them polite. While です works with nouns and adjectives, masu is specifically for verb conjugation.

The basic pattern: Verb stem + masu

To use masu, you need to convert your verb to what's called the masu-form or conjunctive form. This involves taking the dictionary form of the verb and changing it to the stem that masu attaches to.

For example:

How to Make Verbs Polite with ます

Japanese verbs fall into three groups, and each has slightly different rules for forming the masu stem:

Group 1 (u-verbs): Change the final u-sound to an i-sound, then add ます

Group 2 (ru-verbs): Drop the る (ru) and add ます

Group 3 (irregular verbs): Just memorize these

Conjugating ます Forms

The masu conjugation gives you several useful forms:

Present affirmative: ます (masu) = do/does Present negative: ません (masen) = don't/doesn't Past affirmative: ました (mashita) = did Past negative: ませんでした (masen deshita) = didn't

Examples:

The masu form handles both present and future tense, which makes things simpler than English in some ways. Context usually makes it clear whether you're talking about now or later.

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The Key Difference Between です and ます

So what's the actual difference between using masu and desu? This trips up a lot of beginners, but the answer is pretty simple once you get it.

です follows nouns and adjectivesます follows verb stems

You can think of です as the polite copula (the "is/am/are" equivalent), while ます is the politeness marker for action verbs.

Here's where it gets interesting: you can actually use both in the same sentence. For example:

私は学生で、毎日勉強します (Watashi wa gakusei de, mainichi benkyou shimasu) = I am a student and study every day

The で (de) here is the conjunctive form of です, connecting two clauses. The first clause uses the noun 学生 (student), and the second clause uses the verb 勉強する (to study) in its masu form.

What About Using Casual Form Plus です?

Some learners ask about the difference between using ます and using the casual verb form plus です. Here's the deal: you generally don't mix them in standard Japanese.

Correct: 行きます (ikimasu) = I go/will go (polite) Correct: 行く (iku) = I go/will go (casual) Incorrect/Non-standard: 行くです (iku desu)

However, you might occasionally hear constructions like 行くんです (ikun desu), which uses the explanatory ん (n) plus です. This is grammatically correct and adds a nuance of explanation or emphasis. But just slapping です onto a casual verb form without any other grammar doesn't work.

Understanding Politeness Levels in Japanese

The desu/masu form represents what we call the polite form in the Japanese language. This sits between casual speech (using だ and plain verb forms) and more formal or honorific speech (keigo).

When should you use the polite form? Pretty much all the time when you're starting out. Use it with:

You'd switch to casual forms with close friends, family members, or people younger than you in casual settings. But honestly, sticking with desu/masu forms is always safe when you're unsure.

Is the Masu Form Polite?

Yes, the masu form is definitely polite. That's literally its main function. When you conjugate a verb with masu, you're making it appropriate for polite conversation. The casual equivalent would be using the dictionary form or plain form of the verb.

Compare:

Both mean the same thing, but the first one is polite and the second is casual. In a polite conversation, you'd use tabemasu. With your best friend, you might use taberu.

What Is the Masu Form of です?

This question comes up a lot, and it reveals a common misunderstanding. です already IS a polite form. There's no "masu form of desu" because です doesn't work like a regular verb.

です is the polite copula. Its casual equivalent is だ (da). You don't add masu to です because they serve different grammatical functions. です goes with nouns and adjectives, while masu goes with verb stems.

If you're looking for more formal versions of です, you'd use でございます (de gozaimasu), which is the super-polite copula you hear in very formal situations or customer service contexts. But for everyday polite speech, です is what you want.

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Common Mistakes and How to Avoid Them

Let me share some mistakes I see beginners make all the time with the desu/masu form:

Mistake 1: Forgetting です or ます entirely

Beginners sometimes drop the polite ending because they're thinking in English. In Japanese, you need that polite marker when speaking formally.

Wrong: 私は学生 (Watashi wa gakusei) in a polite context Right: 私は学生です (Watashi wa gakusei desu)

Mistake 2: Using です with verbs

Remember, です goes with nouns and adjectives, not verbs.

Wrong: 食べるです (taberu desu) Right: 食べます (tabemasu)

Mistake 3: Double-marking politeness

You don't need both masu and desu on the same verb.

Wrong: 行きますです (ikimasu desu) Right: 行きます (ikimasu)

Mistake 4: Wrong adjective conjugation

With i-adjectives, you conjugate the adjective and then add です. With na-adjectives, you just add です directly.

I-adjective: 高い (takai = expensive) → 高いです (takai desu) NOT 高です Na-adjective: 静か (shizuka = quiet) → 静かです (shizuka desu)

Mistake 5: Mixing politeness levels

Try to stay consistent within a conversation. Don't jump between casual and polite forms randomly.

Mid-Sentence Usage and Advanced Tips

Once you get comfortable with basic desu/masu usage, you'll encounter situations where these forms appear in the middle of sentences, connected by conjunctive particles or clause markers.

The conjunctive form of です is で (de), which you use to connect clauses:

今日は月曜日で、忙しいです (Kyou wa getsuyoubi de, isogashii desu) = Today is Monday and I'm busy

For verbs in masu form, you can use the masu stem (without the ます part) as a conjunctive form to connect actions:

朝起きて、シャワーを浴びて、朝ごはんを食べます (Asa okite, shawaa wo abite, asagohan wo tabemasu) = I wake up in the morning, take a shower, and eat breakfast

Notice how the final verb gets ます but the earlier verbs use the て-form. This is standard: you only need to mark politeness at the end of the sentence in most cases.

When です Appears at the End, Is It Always About Politeness?

Good question. Yes, when です appears at the end of a sentence, it's expressing politeness. That's its primary grammatical function. Even when です seems to add little meaning (like with i-adjectives that are already conjugated), it's still there to make the sentence polite.

However, です can also appear in explanatory constructions like のです (no desu) or んです (n desu), where it adds both politeness and an explanatory or emphatic nuance. But the politeness function is always present when you use です.

Do You Understand How to Use です and ます Now?

Here's a quick decision tree to help you choose:

Step 1: Is this a noun or adjective? → Use です Step 2: Is this a verb? → Use ます Step 3: Am I speaking politely? → Yes, use desu/masu forms Step 4: Am I speaking casually with friends? → Use だ and plain verb forms instead

The more you practice, the more natural this becomes. When you're watching Japanese shows or reading Japanese text, pay attention to when speakers use these forms. You'll start to develop an intuition for it.

A Quick Note About 草 (Kusa)

Why do Japanese people say 草? This is actually unrelated to desu/masu forms, but since it comes up in searches: 草 (kusa) means "grass" but it's also internet slang for "lol" or "haha." It comes from the letter w (used like "lol" because it looks like 笑う, warau, to laugh), and lots of wwwww looks like grass growing. Just a fun aside!

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Putting It All Together: Real Examples

Let's look at some real conversation examples using the desu/masu form:

At a restaurant:

Meeting someone new:

Talking about your day:

Notice how every sentence ends with a polite form? That's the consistency you want to maintain in polite conversation.

Why This Matters for Learning Japanese

Mastering the desu/masu form gives you the ability to communicate respectfully in Japanese from day one. You can have real conversations, ask questions, make requests, and express yourself without worrying about being rude.

The conjugation patterns are regular and predictable once you learn them. Unlike some aspects of Japanese grammar that have tons of exceptions, desu/masu forms follow clear rules. You learn the pattern once, and you can apply it to thousands of verbs, nouns, and adjectives.

Plus, understanding politeness levels helps you grasp Japanese culture better. The language reflects the importance of social relationships and context. Being able to adjust your speech based on the situation shows cultural awareness and respect.

As you progress, you'll learn more casual forms, honorific language, and humble language. But the desu/masu form remains your reliable default for polite, everyday Japanese. Even advanced speakers use it constantly.

Anyway, if you want to practice recognizing desu/masu forms in real Japanese content, Migaku's browser extension lets you look up words and grammar patterns instantly while watching shows or reading articles. You can see these forms in context and build your understanding naturally. There's a 10-day free trial if you want to check it out.