Questions & Answers about Я по-настоящему рад, что мы помирились.
Because рад agrees with я, which is singular.
- рад = masculine singular
- рада = feminine singular
- рады = plural
So:
- Я рад = I am glad (said by a man)
- Я рада = I am glad (said by a woman)
- Мы рады = We are glad
In this sentence, the speaker is one person, so the singular form is used.
Рад is the short form of the adjective радостный? Not exactly in meaning, but grammatically it behaves like a short-form adjective.
In Russian, рад / рада / рады is the normal way to say glad in sentences like this:
- Я рад
- Она рада
- Мы рады
It is used predicatively, meaning it functions like the main description in the sentence, similar to am glad in English.
You would not usually say Я радостный to mean I’m glad. That would sound more like I’m cheerful / joyful by nature or at the moment, not specifically glad about something.