Was not with ではありませんでした

～ではありませんでした ~ dewa arimasen deshita Was not; were not

ではありませんでした (dewa arimasen deshita) means "was not" or "were not". In speech, じゃなかったです is more common.

Level: JLPT N5, beginner
Type: Sentence basics
English links: past of be, negatives, prepositions of time

What it means

This is the past negative: "A was not B". You build it from two parts you already know. Take ではありません (is not) and add でした (was). 学生ではありません becomes 学生ではありませんでした.

It is long, so people shorten it in speech. じゃありませんでした is a little softer. じゃなかったです is very common in polite conversation. With friends, just じゃなかった.

The good news: ませんでした is the same ending that polite verbs use in the past negative. 行きませんでした means "did not go". Learn it once here and you have it for verbs too.

For our students, the hard part is the other way round. Japanese shows "not" and "past" in two separate pieces. English puts both into one short word: wasn't or weren't.

How to build it

Pattern	How it works
A は B ではありませんでした A wa B dewa arimasen deshita	Polite and a little formal. Writing and formal speech.
A は B じゃありませんでした A wa B ja arimasen deshita	Spoken, polite.
A は B じゃなかったです A wa B ja nakatta desu	Very common in polite conversation.
A は B じゃなかった A wa B ja nakatta	The plain form, with friends and family.

Examples

昨日は休みではありませんでした。 kinou wa yasumi dewa arimasen deshita. Yesterday was not a day off.
前の学校は大きい学校じゃありませんでした。 mae no gakkou wa ookii gakkou ja arimasen deshita. My last school was not a big school.
去年、彼は先生じゃなかったです。 kyonen, kare wa sensei ja nakatta desu. He was not a teacher last year.
答えはBじゃなかったです。 kotae wa bii ja nakatta desu. The answer wasn't B.
会議は月曜日ではありませんでした。 kaigi wa getsuyoubi dewa arimasen deshita. The meeting was not on Monday.

How English says it

English says "was not" or "were not", and in speech "wasn't" or "weren't". The subject decides which one, the same as was and were.

Note that "be" does not use "did" for the negative. It is "I wasn't", never "I didn't was". Other verbs use "didn't": "I didn't go". Students must learn to keep the two apart.

Why it can make English hard

Some learners know "didn't" from verbs and use it with "be" as well: "Yesterday didn't a holiday".
One Japanese form covers wasn't and weren't, so students mix them up.
Days and times often need a preposition in English. 月曜日ではありませんでした can come out as "wasn't Monday" instead of "wasn't on Monday".

Mistakes you will hear

Yesterday didn't a holiday. Yesterday wasn't a holiday. "Be" makes its own negative. It does not use "didn't".
My parents wasn't teachers. My parents weren't teachers. A plural subject takes "weren't".
The meeting wasn't Monday. The meeting wasn't on Monday. In English, "on" goes before a day.

In the classroom

Play "Two truths and a lie" about the past: "I was a baseball player. I wasn't a good student." The class guesses, then corrects the lie with wasn't or weren't.
Put two columns on the board: "be" and "other verbs". Write "wasn't / weren't" in one and "didn't + verb" in the other. Point to the columns when students mix them.
Do a quick "not on Monday, on Tuesday" drill with the school calendar. Students fix wrong dates: "The sports day wasn't on Saturday. It was on Sunday."

Practice

Try each one, then open it to check.

1. Fill the gap: 昨日は雨＿。 (It did not rain yesterday.)

Answer: ではありませんでした (or じゃなかったです)

It is past and negative, so ではありません + でした.
2. Change to the past: 学生じゃありません。

Answer: 学生じゃありませんでした。

Add でした to the end of the negative.
3. A student writes "They wasn't my students." Fix it.

Answer: They weren't my students.

"They" takes "were", so the negative is "weren't".
4. Translate into Japanese: It wasn't my bag.

Answer: それは私のかばんではありませんでした。 (or 私のかばんじゃなかったです。)

The noun かばん takes the past negative ではありませんでした.