How to Say “I Didn't” in Japanese: ～ませんでした (Masen Deshita)

Your Japanese teacher asks whether you studied yesterday. You know how to say "I study" and "I don't study," but what if you didn't study yesterday?

The short answer

Use ～ませんでした (masen deshita) to say that you didn't do something. It's the polite past negative ending for Japanese verbs: take ～ません (masen) and add でした (deshita).

The word きのう (kinou) means "yesterday," and べんきょうしませんでした (benkyou shimasen deshita) means "didn't study."

How to make ませんでした: add でした to ません

If you already know how to say "I don't," you're almost there.

Take a polite negative verb ending in ません (masen) and add でした (deshita).

Watch how "eat" changes:

1. たべますTabemasu.I eat.
2. たべませんTabemasen.I don't eat.
3. たべませんでしたTabemasen deshita.I didn't eat.

The action stays the same. Only the ending changes.

You can use this pattern with other familiar verbs.

1. いきませんでしたIkimasen deshita.I didn't go.
2. のみませんでしたNomimasen deshita.I didn't drink.
3. みませんでしたMimasen deshita.I didn't watch.

Once you know a verb's ～ません (masen) form, making its polite past negative is straightforward. It works the same way for every verb, including します (shimasu, "do") and きます (kimasu, "come"): しませんでした (shimasen deshita) and きませんでした (kimasen deshita).

ます, ません, ました, ませんでした: the four polite verb forms

Polite Japanese verbs have four basic endings. Here they are with たべます (tabemasu, "eat"):

• たべます (tabemasu): I eat, or I will eat.
• たべません (tabemasen): I don't eat, or I won't eat.
• たべました (tabemashita): I ate.
• たべませんでした (tabemasen deshita): I didn't eat.

The top two cover now and the future. The bottom two cover the past. ませんでした is the only one that is both negative and past.

Say when it didn't happen: きのう, けさ, せんしゅう

You can use ～ませんでした (masen deshita) on its own when the conversation already makes the time clear.

But adding a time word makes your meaning more specific.

Imagine someone asks what you ate this morning.

Here, けさ (kesa) means "this morning."

You can also talk about yesterday or last week.

1. きのうはコーヒーをのみませんでしたKinou wa koohii o nomimasen deshita.I didn't drink coffee yesterday.
2. せんしゅうはえいがをみませんでしたSenshuu wa eiga o mimasen deshita.I didn't watch a movie last week.

Notice that the time word appears before the action.

You don't need to add a separate Japanese word for "didn't." The negative past ending already expresses it.

ました vs ませんでした: what happened and what didn't

Suppose you're telling a friend about yesterday.

You want to say that you studied, but you didn't watch a movie.

First, compare two sentences about studying.

1. きのうはべんきょうしましたKinou wa benkyou shimashita.I studied yesterday.
2. きのうはべんきょうしませんでしたKinou wa benkyou shimasen deshita.I didn't study yesterday.

The difference is at the end:

• ～ました (mashita) tells us the action happened.
• ～ませんでした (masen deshita) tells us the action didn't happen.

Now combine two different actions.

The word でも (demo) means "but."

You can now describe both things you did and things you didn't do.

Answer "Did you…?" with いいえ、～ませんでした

Imagine your teacher asks whether you studied yesterday.

1. Aきのう、べんきょうしましたかKinou, benkyou shimashita ka.Did you study yesterday?
2. Bいいえ、べんきょうしませんでしたIie, benkyou shimasen deshita.No, I didn't study.

The question uses ～ましたか (mashita ka) to ask whether something happened.

The negative answer uses ～ませんでした (masen deshita).

You don't need to repeat きのう (kinou) in the answer because the question already establishes when the action happened.

ません vs ませんでした: don't use the past for tomorrow

The difference between ません (masen) and ませんでした (masen deshita) matters when talking about time.

Compare these two sentences.

1. あしたはがっこうにいきませんAshita wa gakkou ni ikimasen.I won't go to school tomorrow.
2. きのうはがっこうにいきませんでしたKinou wa gakkou ni ikimasen deshita.I didn't go to school yesterday.

あした (ashita) means "tomorrow," while きのう (kinou) means "yesterday."

The first sentence describes something that won't happen.

The second describes something that didn't happen.

Japanese ～ません (masen) can express both present and future negatives. You don't need a separate future-tense ending.

"I didn't" vs "I haven't yet": まだ～ていません

In English, "I didn't eat" and "I haven't eaten yet" feel close. Japanese keeps them apart.

Use ～ませんでした (masen deshita) when the time is already over. If it's evening and breakfast time has passed, you can say:

But if it's still morning and you plan to eat later, use まだ (mada, "not yet") with ～ていません (te imasen):

Avoid まだたべませんでした (mada tabemasen deshita). ませんでした closes the door on a finished time, while まだ says the door is still open.

Nouns: じゃありませんでした (wasn't)

ませんでした (masen deshita) only attaches to verbs. To say something "wasn't" a noun, use じゃありませんでした (ja arimasen deshita).

Here がくせい (gakusei) means "student." You'll also see the more formal ではありませんでした (dewa arimasen deshita) in writing.

Casual "didn't": ～なかった

With friends and family, people usually swap ～ませんでした (masen deshita) for the casual ～なかった (nakatta).

1. たべなかったTabenakatta.I didn't eat.
2. いかなかったIkanakatta.I didn't go.

You'll also hear ～なかったです (nakatta desu) in everyday polite speech. It's a little softer and less formal than ～ませんでした. Building ～なかった needs the casual ～ない (nai) form, so for now ～ませんでした is your safe, polite choice.

Common mistakes

• Adding でした after ます. Don't use たべますでした (tabemasu deshita) to mean "didn't eat." Start with the negative form たべません (tabemasen), then add でした (deshita).
• Putting ません after ました. The expression たべましたません (tabemashita masen) isn't a valid way to make a past negative. Use たべませんでした (tabemasen deshita).
• Using ませんでした for tomorrow. If you're saying you won't do something tomorrow, use ～ません (masen), not ～ませんでした (masen deshita).
• Confusing verb negatives with です negatives. ～ませんでした (masen deshita) is for polite verb sentences. To say something "wasn't" a noun, such as "wasn't a student," use じゃありませんでした (ja arimasen deshita) instead.

Practise ～ませんでした

Think about yesterday.

Choose three things you didn't do. You might not have studied Japanese, watched a movie, or drunk coffee.

Start with one familiar verb:

Now replace コーヒーをのみませんでした (koohii o nomimasen deshita) with another action.

Next, describe one thing you did yesterday and one thing you didn't do.

Use ～ました (mashita) for the action that happened and ～ませんでした (masen deshita) for the action that didn't.

Finally, answer this question aloud without looking at the example:

If you studied, answer with ～ました (mashita).

If you didn't, answer with ～ませんでした (masen deshita).

Masen deshita: quick questions

What does ませんでした mean?

It's the polite past negative of a verb: "didn't…". たべませんでした (tabemasen deshita) means "didn't eat."

What's the difference between ません and ませんでした?

ません (masen) is for now or the future: "don't" or "won't." ませんでした (masen deshita) is for the past: "didn't."

Is ませんでした polite?

Yes. It's the standard polite form to use with teachers, coworkers, and people you don't know well. Friends usually say ～なかった (nakatta).

How do I say "I haven't done it yet"?

Use まだ (mada) with ～ていません (te imasen), as in まだたべていません (mada tabete imasen). Keep ～ませんでした for a time that's already over.

Keep this in mind

～ませんでした (masen deshita) is the polite ending for actions that didn't happen in the past. Change ～ません (masen) into ～ませんでした (masen deshita), add a time word when useful, and you can start talking about what you didn't do yesterday, this morning, or last week.