「気」 is a kind of energy embodied by your mind and spirit… or so they say. Personally, I really don’t believe in all that mumbo-jumbo but we still have to deal with it because it’s often used in everyday Japanese to describe your mind-set or feelings. In fact, the characters for your emotional feelings 「気持ち」 means 「気」 that is held” and your physical feelings 「気分」 also contains the same 「気」 character.

I’m going to go over some of the most useful and basic ways to use your 「気」 and I don’t mean fireballs and kung-fu moves. Rather, I’ve compiled a list of common expressions that you can use to describe your 「気」. Though making a list of expressions is not usually not my kind of thing, these are so useful and simple (and for some reason often neglected in the classroom) that I feel it’s worth the time to list and describe them. Also, these kinds of expressions are very hard to find in the dictionary unless you almost already know what you’re looking for.

「気」 with verbs so basic, your grandma can use it

Putting aside the image of your grandma firing off hadokens, here is a list of 「気」 expressions with the most simple and basic verbs. I’ve tried to interpret some of the literal meanings as a aid in memorizing what all these kinds of 「気」 means.

1. 気にする – Means to worry about something. It is almost always used in the negative to say, “Don’t worry about it”. The meaning is similar to 「心配しないで」 except 「心配」 involves actual worry and anxiety. 「気にしない」 means don’t even bother paying attention to it or wasting your 「気」.
   

   １）　気にしないで – Don’t worry about it.

2. 気になる – Similar to 「気にする」 except instead of bothering about something, it’s becoming a bother. In other words, it’s something that is niggling your subconscious and making you wonder about something.
   

   １）　彼女の歳が気になる。 – I wonder what her age is. (lit: Her age has been bothering me.)

3. 気がする – Your 「気」 is acting up and alerting your senses. As a result, you have a feeling of whatever you attach 「気がする」 to.
   

   １）　もう終わった気がする。- I have a feeling that [it] already ended.

4. 気がつく （気づく） – Your 「気」 attaches to you making you regain consciousness in the literal sense or in a figurative sense of just waking up and smelling the coffee.
   

   １）　気がついたら、もう９時になっていた。 – When I came to my senses, it had become 9:00 already.
   ２）　彼は全然気づいていない。 – He doesn’t realize (or hasn’t noticed) it at all.

5. 気をつける – Attach your 「気」 and always keep your wits about you. In other words, be careful.
   

   １）　気をつけて！ – Be careful!/Take care!

6. 気をつかう – Use your 「気」 to pay attention to or attend to somebody. A good host always uses her 「気」 for her guests and their needs.
   

   １）　気をつかってくれて、ありがとう！ – Thanks for caring about me!

7. 気にいる – This is a curious one as it uses the not-so-common 「いる」 reading of 「入る」. It is usually used in the past tense as 「気に入った」, literally meaning something entered your 「気」. This essentially means it came to your liking. It’s a shorter, easier, and more casual way to say the same thing as 「好きになった」. If you use a Japanese browser, you might also have noticed that the bookmarks are called 「気に入り」.
   

   １）　これ、気に入ったよ。 – This has come to my liking.

   (Thanks Florian for suggesting this one be added to the list.)

Conclusion

I’ve tried to keep my list short and simple to prevent this from becoming a monster list with too much information. However, if you’re in the mood, you can scroll through a huge list by going to WWWJDIC, search for 「気」 and set the checkmark for “Starting Kanji”. You’ll get all sorts of useful expressions like 「気が強い」、「気が向く」、「気が散る」、etc., etc. Someday, you can become a master of at least talking about your 「気」 without even having to work out!