The Japanese suffix ーがる is one of those things you aren’t too likely to learn about in a beginner Japanese course. You may have seen it in a advanced textbook if at all.
I understand the reason for not introducing this expression until a student has more experience with the language’s fundamentals. After all you won’t hear ーがる all that often and it isn’t critical to get by in day-to-day life. However, like most grammar constructions that be used in many different situations, the earlier you get a handle on this expression the more ways you can express yourself.
ーがる can be used after i-adjective (whose final い is removed), and occasionally after a na-adjective (with no な in between). In both cases it turns the word from an adjective to a verb which expresses feeling like or looking like that adjective. It’s important to note that がる in this case is conjugated like any other verb (がって／がった／がらない／etc)
- John was in in room by himself feeling lonely.
- You don’t need to be embarrassed. (lit: “It’s ok if you aren’t embarrassed”)
- The baby wants the candy. (or “The baby looks like he/she wants to candy”)
- The dog looks like he doesn’t like the customer.
Remember ーがる changes an adjective from simply defining a state, feeling, or condition, into something that is actively being felt by a person, or the impression that they are feeling something. There is always an implicit subject, stated or otherwise.
This ending can be used for all sorts of adjectives, though as always it’s best to listen for whatnative speakers use and emulate that in your own speech and writing.
A commonly used word with a slightly different nuance is the word 可愛がる, which though literally means “to feel something is cute”, extends beyond that to meaning someone treats the object as if it is cute. The English translation differs case-by-case, but sometimes can be expressed as “pamper”.
- Tommy is always pampered by his parents.
In rare cases, ーがる can instead mean “to act as if”, as in the word 強がる which means to act tough or strong.
- She acts tough when she is with a boy she likes.
ーがりや (sometimes written がり屋） is a related expression which means a person who is apt to act or feel a certain way. Sometimes it is followed by さん.
- 恥ずかしがりや ー Someone who gets embarrassed easily
- 寂しがり屋 さん ー Someone who gets lonely easily
A final use of ーがる is when it is added to the end of a verb in the ーたい form to make ーたがる. This means that it seems like someone or something looks like they want to do a certain action.
- It looks like the bird wants to eat the bug
You may have noticed that all of these examples are when talking about a third party. If you were speaking about yourself, you wouldn’t say “I look like I want to eat” since you know whether you actually do or not. So it is natural to say 食べたい regarding yourself instead of 食べたがらない which would be awkward.