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When used with the particle て, いる functions as a supplementary verb. In Japanese a supplementary verb is a verb that loses some or all of its literal connotations to serve (a) specific grammatical purpose(s). Although it retains some resemblance to its basic meaning of indicating state, ～ている should be treated separately from いる.

 Correctly interpreting ～ている depends on the verb being used with it. Therefore, pay attention to the kinds of verbs used for each meaning introduced in this lesson. "Kind" here does not refer to how the verb conjugates, but rather what it means semantically and its relation to verbs of similar meaning.  

 -ing

The first usage of ～ている equates to "-ing." You're doing something, thus it is a continuation in the present time. This is also linked to ongoing action, which is typically expressed with verbs of process--食べる、飲む、走る. 

1. 太朗たろうは朝ご飯を食べています。
     Taro is eating breakfast.

2. 教師きょうしをしています。
    I am a teacher. 

Phrase Note: Remember that using ～をする in this manner shows profession and is more appropriate in this situation than です.

 Habit

Then there are instances when the action is not literally being done now, but it's a habit of some sort.

3. A学校に行っています。
     I go to School A. 

4. 天才てんさいはいつも勉強に打うち込こんでいる。
    Geniuses are always diving into studies. 

 State of Being

When used with verbs like 着る (to wear), it shows a state of being dressed. This is in contrast to putting clothing on, which has to be expressed differently to avoid ambiguity as 着ている最中さいちゅう. Other verbs are just like this.  

5. ネクタイが曲まがっている。
    His necktie is tangled. 

6. 古着ふるぎを着ています。
    I'm wearing old clothes. 

 State: Motion Verbs

For verbs of motion like 行く and 帰る, it shows state of having done that movement. Interpret it as a completed action and the result being the state in effect.

7. 彼女は東京に来ています。
    She has come to Tokyo.

8. 彼はもう帰っている。
    He's already gone home.

More Examples

9. 赤い顔をしている。
    To have a red face. 

10. 彼女は長い髪かみをしている。
      She has long hair. 

11. 私は東京駅えきの近くに住んでいます。
      I live near Tokyo Station.

12. 彼は会かい長ちょうをしていた。
      He had been the chairman.

Nuance Note: 会長 is a chairman of an organization; 議長ぎちょう is a chairman of an assembly. 

13. お母かあさんによく似にています。
      You resemble your mother well. 

Word Note: お母さん is used instead of 母 because the speaker is referencing the listener's mother.

14. その橋はしは石でできている。
      The bridge is made of stone. 

15. この机は壊こわれています。
      This desk is broken. 

16. 砂糖さとうはもう入はいっています。
      Sugar has already been put in. 

17. 今日も穏おだやかなお天気が続いていますね。
      The moderate weather is continuing today, isn't it? 

18. 小屋こやは山へ面めんしている。
      The lodge faces the mountain. 

19. 彼は通りをのそのそと歩き続けていた。
      He continued to flop along the street. 

20. その教科書は初学者しょがくしゃに適てきしています。
      The textbook is suitable for beginners. 

21. お風呂ふろはもう沸わいていますか。
      Is the bath hot yet? 

21. その時計(とけい)は5ご分ふんほど進すすんでいます。
      The clock is five minutes fast. 

22. 私は車を持っています。
      I own a vehicle. 

23a. 木になっていたリンゴを集めた。〇
23b. 木にあっていたリンゴを集めた。X
23c. 木にあったリンゴを集めた。??
        I gathered the apples that were on the tree. 

Word Note: This なる is 生る, which means "to bear fruit". So, this sentence more literally reads "I gathered the apples that ripened on the tree". If you were to say the third line, it sounds like the apple is somehow out of place inside a tree. It definitely isn't talking about picking apples from an apple tree. 

24. 町は谷たにに位置いちしている。
      The town lies in the valley. 

25. 山がそびえている。
      The mountain towers above (everything).

漢字 Note: そびえる in 漢字 is 聳える, but you don't need to know this spelling for now.  

26. 疲つかれています。
      I'm tired. 

27. 明治大学で法律ほうりつを勉強しています。
      I am studying law at Meiji University.

28. 今晩空あいている部屋へやはありますか。
      Do you have any vacant rooms this evening? 

29. この金額きんがくは総合保険そうごうほけんを含ふくんでいますか。
      Does this price include fully comprehensive insurance? 

30. 彼は電流でんりゅうを流ながしている。
      He's passing an electric current.

31. 通りは込んでいる。
      The road is crowded.

Attribute Note: When 込んでいる is an attribute, it's often just 込んだ. Also, you wouldn't use 込む to describe Tokyo or Japan. You could say 東京はどこへ行っても込んでいる, which means "Tokyo is crowded wherever you go".

Spelling Note: This usage of the verb 込む can also be spelled as 混む.

32. 存在そんざいしている。　?

Phrase Note: The above phrase is only used when telling for how long something has existed.

33. 数かずでは圧倒あっとうしている状態じょうたいだ。
     As far as numbers are concerned, the situation is overwhelming. 

～ている Negation

     The negative is ～ていない, but ～ず（に）いる and ～ないでいる mean "without...-ing". ～ずにいる is used in more formal, poetic-like speech.

34. 覚えていません。
      I don't remember.

35. 僕ぼくは何もしていません。(男性語)
      I'm not doing anything. 

36. 決けっして病気にならないでいることは不可能ふかのうだ。
      It is impossible to never get sick.  

37. 彼はいつも落おち着つかないでいる。
      He is always ill at ease. 

38. 彼女は通かよえないでいる。
      She has not been able to go to school. 

Grammar Note: 通える is the potential form of the verb 通う.

Contractions 

～ている is usually contracted to ～てる in casual conversation. Even in polite speech, it is commonplace to hear ～てます instead of ～ています. However, in truly polite situations such as being in an interview, it is NG (エヌジー ＝ No good) to use such contractions as humanly possible.

Dialect Note: In other regions of Japan, you will hear ～とる or even ～ちょる instead of ～てる. These are both contractions of ～ておる, which in Standard Japanese is the plain humble form of ～ている. However, in the dialects these variants are used, they are treated as the standard non-honorific form for conversation purposes. 

39. 今の、聞いてましたか。（ちょっとくだけた話し言葉）
     Were you listening to what I was saying just now? 

40. 父は私が何を勉強してるか知らない。
      My dad doesn't know what I am studying.

41. 動いてる！
      It's moving.

Word Note: 動く is "to move " as in to physically move about, not "to move to a different house". That meaning of the English verb "to move" is carried out by the verb 引っ越こす.

States & Appearances　　状態・様子

In the chart below, several verbs are shown in different forms. For each row, the same verb is used, but for each column, the grammar pattern being used is different. 

Grammar Notes:

1. ～た　is often preferred over ～ている when used as an attribute. You can substitute it and still create a grammatical phrase, but 90% of the time, ～た is used.

2. Context determines whether ～ている is the 進行形しんこうけい(progressive) or the 完了形かんりょうけい(perfect tense).

漢字 Note: やせる has 漢字 spellings 痩せる・瘦せる・瘠せる, and they are listed in usefulness. But, you're not responsible for any of them. They all show up in books, though. ひび has the spelling 罅, which although cool looking, is not very useful to remember.