A1
ました — the past
How to form the past tense of Japanese verbs and adjectives, including the negative past, and why Japanese needs only one past form.
ます becomes ました. That is the whole rule for polite verbs.
食べました。
Tabemashita.
I ate.
昨日映画を見ました。
Kinō eiga o mimashita.
I watched a film yesterday.
One past tense covers several English ones
I ate, I have eaten, I had eaten all land on ました. Japanese does not distinguish them grammatically; where the difference matters, an adverb carries it — もう (already), まだ (not yet).
もう食べました。
Mō tabemashita.
I’ve already eaten.
The negative past
ませんでした — the negative plus でした, stacked in that order.
行きませんでした。
Ikimasen deshita.
I didn’t go.
It is the longest of the four basic forms and the one most often shortened in speech to 行かなかった, the plain equivalent.
い-adjectives
They take かった, on the adjective itself.
寒かったです。
Samukatta desu.
It was cold.
面白くなかったです。
Omoshiroku nakatta desu.
It wasn’t interesting.
寒いでした。
寒かったです。
The tense belongs to the adjective. 寒い → 寒かった, and です is left in the present carrying politeness only. See adjectives.
Nouns
でした, which is the past of です.
学生でした。
Gakusei deshita.
I was a student.