Form, Tense
suffix
The kanji and the word share one of the same meanings: form. It doesn't just mean form though, it means tense too. Like verb tense.
けい
This has the same reading as the kanji you learned, meaning you know the reading!
「出る」の「て形」は「出て」です。
The te-form of "deru" is "dete."
会社では、です・ます形を用いてコミュニケーションをとります。
In the company, we communicate using the desu/masu form.
「大切な人だった」？どうして今、カコ形で言ったの？
"You were an important person?" Why did you say it in the past tense?