When we learned about the copula verb だ, we learned how it is the "to be" verb in Japanese when talking about how "X = Y." An application of "to be" in English that does not exist for だ, though, is when talking about "there is X." In this scenario, there are primarily two verbs that come to mind: ある and いる.
Both verbs establish the existence of things, but what sets them apart and how they are sometimes interchangeable can be confusing.
Of the two verbs, ある is the most basic and fundamental to describing existence. Before delving into how it is used semantically, let's review how it conjugates.
The verb ある is a slightly irregular R-Type Godan Verb because of how it lacks a plain negative form. Instead, that role is completely taken over by the adjective ない, which means for "there to not be." Consequentially, ある's basic conjugations are:
Conjugation | Plain Speech | Polite Speech |
Non-Past |
ある |
あります |
Past |
あった |
ありました |
Negative |
ない |
ないです ありません (Politer) |
Negative Past |
なかった |
なかったです ありませんでした (Politer) |
The verb いる is a regular Ichidan verb whose basic conjugations are as follows:
Conjugation | Plain Speech | Polite Speech |
Non-Past |
いる |
います |
Past |
いた |
いました |
Negative |
いない |
いないです いません (Politer) |
Negative Past |
いなかった |
いなかったです いませんでした (Politer) |
In Modern Japanese, いる is primarily used to mark the existence of something that is both animate (moving or capable of moving) and alive (or at least made out to be alive).
32. 佐藤さんは家にいませんでした。
Mr. Sato was not at home.
33. この公園にはいろんな動物がいます。
There are all sorts of animals in this park.
34. 50頭を超えるゴリラがいました。
There were over 50 gorillas.
35. 神様はいつもあなたのそばにいます。
God is always right by your side.
However, as its Kanji spelling 居る implies, it can be used to broadly demonstrate the existence of anything on the move, while also simultaneously indicating where it is in time and space. This is why it is so commonly used in reference to vehicles.
36. バスはまだバス停にいると思いますよ。
I believe the bus is still at the bus station.
37. 隣の車線にクレーン車が居ると、倒れてくるのではないかと疑問に思ってしまう。
Whenever there is a crane in the adjacent lane, I wonder whether it's going to come collapsing down.
38. 追い越し車線に車が数台いる。
There are several cars in the passing lane.
39. 明星がいる。
There is the evening star, Venus.
Etymology Note: The original meaning of 居る was as the antonym of 立つ meaning "to stand." That being said, its ability to refer to things moving about predates its ability to refer to living things that happen to be stationary. However, because living things are generally on the move, that is how it eventually became associated with the living. For trees, though, which are living but always stationary, only ある is used as "living" was an added condition to the use of いる to its already existing prerequisite of being with something animate.
いる is till heavily correlated with living objects. It will often be used as a synonym of 住む meaning "to live (at)."
40. 兄はロンドンにいます。
My older brother is (living) in London.
Similarly to ある, いる may indicate the possession of living things. This is most often used to demonstrate blood relationships.
41. 私(に)は一人も兄弟がいません。
I don't have a single sibling.
Speakers do at times extend this nuancing to pet ownership, but the verb 飼う meaning "to raise (an animal)" is preferred. A factor as to why this is can be explained by the inherent ambiguity had by using いる between "there just being an animal" versus actually owning one.
42. 犬がいません。
There isn't a dog.
Without any context, いる will default to a simple statement on existence.
43. 我が家には3羽います。
[There are/we have] 3 birds in our home.
Upon having learned the individual meanings of ある, it would seem that いる is grammatically unnecessary to express existence at all if ある can already state the existence of anything.
Although that was most certainly the case in older stages of the language in which いる didn't start out as an existential verb, the associations that they respectively currently have dictate how a sentence is interpreted when either happen to be possible.
ある VS いる: Scenarios of Overlap
Whenever there is overlap between ある and いる, it is not the case that the feeling of the sentence remains unchanged upon swapping one out for the other.
44. 人形がいっぱい{いる・ある}ね。
There are lots of dolls, aren't there?
Sentence Note: いる is used in situations as handling dolls when the speaker hinges toward how human-like they are.
45. あそこにロボットが{います・あります}。
There is a robot over there.
Sentence Note: When robots are truly human-like and are very much animate, いる is more than acceptable if not preferred despite not being alive.
46. あそこにバスが{いる・ある・止まっている}。
There is a bus over there.
Sentence Note: As discussed earlier, いる gives the implication that the bus has been in transit and that the speaker is describing its temporary stationary state. Otherwise, ある or a reasonable paraphrase such as "is stopped" = 止まっている will be more appropriate.
Although ある in certain literary contexts, almost certainly written with an emphatic Kanji spelling to go along, can mean "to be alive," in scenarios in which it contrasts with いる, the entity is 'dead' or at least not in the realm of the living with ある.
However, due to understandable sensitivities that people have towards fellow human beings being no longer with us, いる is overwhelming preferred when referring to the deceased.
47. ピーナッツのアレルギーで死んだ人が{いました・ありました}。
There were people who died from peanut allergies.
As for deceased pets, people generally refrain from using ある for similar reasons. Most people don't want to intentionally sound morbid.
48. 毒入りのものを食べて死んだ猫が{いた・あった}。
There was a dead cat that ate something laced with poison.
As for dead animals in a generalized scenario detached from human emotions, ある is preferred, but of course, people who have deeply held beliefs about the death of any living thing may wish to not follow this norm. Also, there is nothing wrong with paraphrasing ある・いる of the sentence in such a situation.
49. コップの中に死んだ蝿が入っている。
There is a dead fly in my cup.
Another word to consider is 怪我人 meaning "injured." Though it is a noun relating to people, ある can still be used as an extension of how it is used to note the occurrence of something. Meaning, "injuries occurring" is equated with "those injured." In general, when ある is used with living people, the people are being stated in an abstract sense void of emotional attachment.
50. 乗客の中に怪我人は{いませんでした・ありませんでした}。
There were no people injured among the passengers.
51. 妻子の{ある・いる}人{が・を}好きになってしまいました。
I've ended up liking a person with a wife and kid(s).
52. 神が{ある・いる・存在する}。
[There is/are god(s)/kami/God(s)/kami exist].
Sentence Note: Ignoring the various interpretations of the word 神, describing a spiritual entity with いる is most common in modern speech, but that does not detract from the grammaticality of using ある, especially when spelled as 存る. As for the use of 存在する, this is the formal word for "to exist."
Returning back to Ex. 31, 31a reflects how ある was widely used to express the existence of people in slightly older Japanese. In typical spoken language, this sentence would be rendered in various ways: by switching to いる, paraphrasing out the existential verb (31c), or using おる, which is a dialectal variant of いる that is incredibly common throughout Japan.