Noun and Adjective Conjugation

Another grammar point I learned semi-recently is conjugation of nouns and adjectives to show state of being for present/past and positive/negative. This is something I need more practice with so I don't have to stop and think about a conjugation for five minutes each time I want to speak.

Nouns and na-adjectives:

Present positive: 犬
Present negative: 犬じゃない
Past positive: 犬だった
Past negative: 犬じゃなかった

These are saying the following, in order:

Dog
Not a dog
Was a dog
Was not a dog

I'm not sure why we're having a discussion on whether someone was a dog, but there you go. Even though 犬 is a noun, the exact same conjugation rules would apply with a na-adjective like 簡単. You just add the appropriate ending to the word and you're done.

I-adjectives:

Present positive: 忙しい
Present negative: 忙しくない
Past positive: 忙しかった
Past negative: 忙しくなかった

Busy
Not busy
Was busy
Was not busy

These are a bit more complicated, but all you do is drop the last い and then add the appropriate ending, just like we did above.

I'm going to practice a few sentences with various conjugations and some other grammar to cement my understanding of it.

あれは、猫じゃなかった。
That was not a cat.

アリスさんは、忙しくないよ。
Alice isn't busy, you know.

今日の授業は、面白かったね。
Today's class was interesting, huh?

リーさんは、あまり楽しくないね。
Lee isn't very fun, is he?

ジー二さんは、とても静かだよ。
Ginny is very quiet.

Here I've tried to incorporate usage of the particles ね and よ, which add a more conversational feel to the sentences.

Credit goes to Tae Kim's lessons seen here and here.