Grammar Point
Godan verb with 'ru' ending
v5r 
suffix
suf 
がる

to show signs of being, to feel, to think

following adj. stem

Adjective stem + がる

The auxiliary verb がる is attached to the stem of an adjective to describe the outward signs or behavior of someone else (a third person) who appears to be feeling a certain way. It transforms an internal feeling or physiological state into an observable action or tendency.

い-Adjective stem + がる

For い-adjectives, remove the final い and add がる.

He is acting like he is cold.

The child is acting scared.

な-Adjective stem + がる

For な-adjectives, use the base stem and add がる.

She is acting like she dislikes / is reluctant.

Note

がる is primarily used for third-person subjects because you cannot directly know another person's internal feelings, only their outward behavior. It is used with psychological adjectives like ほしい (want), 怖い (scared), or physiological ones like 寒い (cold). When used in the form がっている, it describes a current state or behavior.

Words: 
がる
Radicals of radicals