Questions & Answers about Он всегда дружелюбный, даже когда устал.
In Russian, the verb to be is usually omitted in the present tense.
So:
- Он дружелюбный = He is friendly
- literally, it looks like He friendly
This is completely normal in Russian.
You only use forms of быть more often in the past or future:
- Он был дружелюбный = He was friendly
- Он будет дружелюбный = He will be friendly
So in the present, leaving out is is the standard pattern.
Дружелюбный is an adjective, and it has to agree with the person it describes.
Here the subject is он = he, so the adjective is:
- masculine
- singular
- nominative
That gives дружелюбный.
Compare:
- Он дружелюбный = he is friendly
- Она дружелюбная = she is friendly
- Оно дружелюбное = it is friendly
- Они дружелюбные = they are friendly
So the ending -ый here matches он.