The past negative ませんでした

Verb ませんでした verb masen deshita Did not

ませんでした (masen deshita) is the polite past negative: 行きませんでした, "I didn't go". Add でした to the ません form.

Level: JLPT N5, beginner
Type: Verb forms
English links: past simple negatives, auxiliary do, short answers

What it means

Take the negative ません and add でした (was). 行きません becomes 行きませんでした, "I didn't go". It is long, but it is regular for every verb.

Use it for something that did not happen at a finished time: yesterday, last week, this morning. 昨日は学校に行きませんでした.

For "not yet", Japanese uses a different pattern: まだ食べていません (I haven't eaten yet). ませんでした says the chance is over. ていません says it may still happen. You will meet ています later in this list.

With friends, the short form is 行かなかった. In the staff room, ませんでした is the safe choice.

How to build it

Pattern	How it works
～ません + でした (食べません → 食べませんでした) tabemasen → tabemasen deshita	Add でした to the negative.
行きます → 行きませんでした ikimasu → ikimasen deshita	Group 1 verbs follow the same rule.
します → しませんでした, 来ます → 来ませんでした shimasu → shimasen deshita, kimasu → kimasen deshita	The irregular verbs are regular here too.

Examples

昨日は学校に行きませんでした。 kinou wa gakkou ni ikimasen deshita. I didn't go to school yesterday.
今朝は朝ごはんを食べませんでした。 kesa wa asagohan o tabemasen deshita. I didn't eat breakfast this morning.
宿題をしませんでした。 shukudai o shimasen deshita. I didn't do my homework.
山田さんはパーティーに来ませんでした。 yamada-san wa paatii ni kimasen deshita. Ms Yamada didn't come to the party.
週末はテレビを見ませんでした。 shuumatsu wa terebi o mimasen deshita. I didn't watch TV at the weekend.

How English says it

English uses "did not" or "didn't" with the base form of the verb: "I didn't go". The past is shown once, on "did". The main verb does not change.

So "didn't" works for every verb, regular or irregular. That is good news for students, once they trust it.

Why it can make English hard

Students mark the past twice: "didn't went". They have just worked hard to learn "went", so they want to use it.
ませんでした ends in でした, which students know as "was". Some reach for "was" or "wasn't" with a verb.
Japanese has no helper verb, so some beginners put "not" straight before a past verb: "I not watched".

Mistakes you will hear

I didn't went to school. I didn't go to school. "Did" carries the past. The main verb goes back to the base form.
I wasn't do my homework. I didn't do my homework. でした sounds like "was", so the student reaches for "was". With a verb, English uses "did".
I not watched TV. I didn't watch TV. English needs the helper "did". Japanese has nothing like it.

In the classroom

Write "did + not + base verb" as a simple formula on the board. Then show that "didn't went" breaks it. Students like a rule they can check themselves.
Play "Find someone who didn't...". Students ask "Did you eat breakfast today?" and answer "No, I didn't." or "Yes, I did." Short answers drill the helper.
When a student says "didn't went", just say "didn't go?" with a smile. A quick echo works better than a long correction.

Practice

Try each one, then open it to check.

1. Make the past negative: 読みます

Answer: 読みませんでした

Change ます to ません, then add でした.
2. Fill the gap: 昨日、テレビを見＿。 (I didn't watch TV yesterday.)

Answer: ませんでした

Past and negative together.
3. A student writes "I didn't finished my homework." Fix it.

Answer: I didn't finish my homework.

"Didn't" already shows the past. Use the base form.
4. Translate: 田中さんは来ませんでした。

Answer: Mr Tanaka didn't come.

Past negative: "didn't" + base form "come".