ARU AND IRU (ある / いる)
ARU (ある) is used to express the existence of what is inanimate (objects, events, etc.). On the other hand, IRU (いる) is used to express the existence of what is animated, i. e. living beings. The subject is almost always referred to by the particle GA (が). The topic of the sentence can be omitted when the context is obvious, as in the following example:
|Kyou wa tesuto ga arimasu.|
|I have a test today.|
Literally: Concerning today, a test exists.
The sentence could very well mean "We have a test today", and concern a group of people like a class, and no longer me alone. Or simply "Today, there is a test". The Japanese language tends to imply information that can be understood only by the context. If means that outside any context, sentences can often be translated in different ways.
It should also be noted that it's not necessary to use the particle WA (は) (which indicates the topic of the sentence) after the adverbs of time (today, tomorrow, yesterday, etc.). In our example above, we could have written 今日 instead of 今日は, but は emphasizes the information.
ARU (ある) and IRU (いる) can often be translated as “there is.”
|Watashi no mae ni inu ga imasu.|
|There is a dog in front of me.|
Literally: Before me, a dog exists.
A dog is a living being, so いる is used. But be careful, Japanese grammar does not consider flowers or plants as animated beings, and requires the use of ある.
|Niwa ni wa hana ga takusan aru.|
|There are many flowers in the garden.|
Literally: In the garden, many flowers exist.
In that sentence, ある is in the plain form (also called the dictionary form). But, of course, it's possible to conjugate it to express the past tense, negative form, or the future tense with the use of a word expressing time. If we take the same examples as above:
|Kinou wa tesuto ga arimashita.|
|Yesterday I had a test.|
Respectively, in the polite form with the use of -MASU (-ます). ARIMASU (あります) becomes ARIMASHITA (ありました) in the past. And the plain form ある becomes ATTA (あった) in the past tense.
|Watashi no mae ni inu ga imasen.|
|There isn’t any dog in front of me.|
Same process as above. The polite form IMASU (います) becomes IMASEN (いません) in the negative form. And the plain form いる becomes INAI (いない) in the negative form.
|Niwa ni wa hana ga amari arimasen deshita.|
|There weren’t many flowers in the garden.|
The polite form ARIMASU (あります) becomes ARIMASEN DESHITA (ありませんでした) in the past negative form. And the plain form ある becomes NAKATTA (なかった) in the plain negative form.
Here is the detailed conjugation:
At last, to express the future:
|Ashita wa tesuto ga arimasu.|
|Tomorrow, I’ll have a test.|
Literally: Tomorrow, a test will exist.
The presence of the adverb of time 明日 (ashita, tomorrow) at the beginning of a sentence expresses the future. It’s also possible in Englishto use the present tense when speaking (tomorrow, I have a test). But in Japanese, the future (grammatically and syntactically speaking) doesn't exist, it's replaced by the present tense.