The "Key" to Particles
Your 気 is your "vitality," your "spirit," your "energy." It's hard to find an English word that perfectly captures the essence of 気.
To make matters more complicated, 気 also appears in a whole slew of idioms. And these idioms just so happen to make use of a wide variety of particles.
As such, exploring some idiomatic phrases using 気 is a nice way for us to also explore the functions of various particles.
Time to dive in...
気をつける (きをつける // to be careful; to take caution)
The verb つける has too many meanings to count. Generally speaking, however, it can help to think of it as meaning something like "to affix" or "to attach."
When you "affix your 気 (to yourself)," you are being careful.
Makes sense... I guess...
Since つける is a transitive verb, and our 気 is the thing we are "affixing," we say 気をつける. We learned to use を with transitive verbs back in this lesson, yeah?
To see how this phrase is used, let's say you just went out with some friends, and now one of them is going home. As he walks away, you tell him:
Be careful. // Get home safe.
Literally: "be careful (and) + ね."
気がする (きがする // to feel [that]; to sense [that]; to have a feeling [that])
You know when you have that feeling that someone is watching you?
How about when you feel like you heard something in what should be an empty room?
What does it mean to "feel" these things? Could it be said that your "spirit" or "energy" is doing something? Perhaps this intangible piece of your inner self is moving around, saying "!!!"
If that sounds somewhat reasonable, then perhaps this Japanese phrase does, too.
When your 気 "does (=する)" something, you are feeling something. This 気 is performing the action of する, so it is the subject of our phrase, which is why we use the particle が. This might make sense if you remember our lesson on the (sub)zero pronoun.
Anyway, let's say that you heard something in the room beside yours — a room that should be empty! You could say:
いま なにか きこえた きがする。
I feel like I just heard something.
Literally: "now + something + heard / was audible + have a feeling."
気にする (きにする // to worry about; to care about; to be concerned about)
Do you care if someone makes fun of your hair? If so, you are "making (=する)" that "into (=に)" your 気.
I'm not sure how much sense that makes, but, yeah, the phrase 気にする is used in this type of situation... and it's very, very common.
For example, let's say that you lent your friend a book of yours. Today she tells you that she lost it and apologizes. You're an awesome, easy-going, and forgiving person, so you say:
Don't worry about it.
Literally: "don't worry about (and)."
↑ I recommend memorizing this phrase as is. You'll find chances to use it, I'm sure... although I suppose that's true of all of the phrases in this lesson.
気になる (きになる // to be worried about; to be concerned about; to be curious about)
Just looking at the meaning of this phrase, you might think that it's interchangeable with 気にする. It is NOT!
You are in control of whether or not you 気にする something, but you are not in control of whether or not you 気になる something.
Looking at the verb, this makes sense. なる means something like "to become." So, when something "becomes your 気," you can't help but worry about it, think about it, be concerned about it.
As to why we use に, well, the verb なる is always preceded by the particle に. This makes sense because the verb "to become" implies a transition or change — that is, it implies a movement to a new state (i.e. a new "destination"), and we mark such things with the particle に.
You'll find that the meaning of 気になる is pretty versatile.
For example, it can be used when you are "worried" about something bad. Let's say your mom is sick, you could say:
はは の こと が きになって ねむれない。
I'm so worried about my mother that I can't sleep.
Literally: "mother + の + thing + が + am worried about (and) + cannot sleep."
Are you wondering why we used the verb 眠る (ねむる // to sleep) in the above sentence instead of 寝る (ねる), which we can also translate as "to sleep" and saw in previous lessons?
So, yeah, 気になる can be used when you are "worried about" something.
But it can also be used when you are "interested in" something.
For example, let's say that you just finished the last episode of your new favorite show on Netflix. Unfortunately, the next season hasn't been released yet! And, as is always the case, there was a real cliffhanger ending, and you absolutely must know what's going to happen. You say:
I wanna know what happens! // I'm curious about what's gonna happen!
Literally: "continuation + am curious about!"
To give another example, let's say that your significant other says that they just ordered your birthday present, but they won't tell you what it is yet. You say:
I wonder what it is...
Literally: "am curious about + な～. "
気に入る (きにいる // to like [e.g. a present])
This phrase is used when you like something, especially something new that you have been given or experienced.
For example, after giving your friend a present, you might ask:
Do you like it?
Literally: "like (and) + gave (me)?"
I think I'll never get over the fact that 入る in the phrase 気に入る (きにいる) is pronounced いる and not はいる.
In isolation, it's pretty safe to assume that 入る is the verb 入る (はいる // to enter; to go into).
For example, if you just met your friend outside of the café where you're going to have lunch together, and you're chatting on the sidewalk for a bit, after a while you could motion toward the door and say:
Wanna go inside?
These are not the only idiomatic phrases that use the character 気. We'll come across more in our studies.
Likewise, we'll come across more (and often more confusing) uses of the particles shown above. I don't think that's necessarily a big deal, though. 99.9% of my understanding of particles came from simply seeing and hearing them used in thousands of different sentences in thousands of different situations.
It's hard to explain why we might use a certain particle in an idiom, for example. But once you hear people use that idiom enough times, it just starts to feel natural.
Long story short, 気にしないで！