When an い-adjective ends in 〜かった, we know it is in the past tense. い-adjective かった can take です to show politeness, but be careful not to use the past tense marker でした!
What Is the Past Tense Form of い-Adjectives?
When い-adjectives are in the past tense, they end in 〜かった. While in English, tense must be indicated by a verb (as in was fun), い-adjectives conjugate to take the suffix 〜かった to accomplish the same thing. Let's see how this works:
楽し
い+ かった = 楽しかった
As you can see, this conjugation is quite simple. Remove the present tense ending 〜い on the end of the word (楽しい → 楽し), and then add 〜かった (楽し → 楽しかった). We also wrote about using past tense い-adjectives here.
Other Forms of い-Adjectives
Check out the chart below to see how 〜かった fits into the い-adjective paradigm. Click on other conjugations or forms to learn more about them!
| Form | 日本語 | English |
| Stem Form | 強 | |
| く Form | 強く | strongly |
| て Form | 強くて | strong, (and) |
| Present Tense Form | 強い | is-strong |
| Past Tense Form | 強かった | was-strong |
| Negative Form | 強くない | is-not-strong |
| Past Negative Form | 強くなかった | was-not-strong |
| Conditional Form | 強ければ | if strong... |
| Measurable Noun Form | 強さ | strength |
| Subjective Noun Form | 強み | strong point |