In Japanese, the word “I” (私;わたし;Watashi) is used in formal and also informal contexts in both writing and speaking. While this is the most common word for “I”, there are three other words meaning “I”. 「あたし；Atashi 」is a word used informally, especially in spoken languages to mean “I” by female speakers. 「僕；ぼく；Boku」is used both formally and informally by male speakers. 「俺；おれ；Ore」is used informally by male speakers. While it may be the case that these words can be gender-neutral words in contexts like manga and novels, it is important to distinguish them and use in appropriate contexts. Also, by adding 「たち；Tashi」, the meaning becomes “We”, so 「私たち；わたしたち；Watashitachi」, 「あたしたち；Atashitachi」, 「僕たち；ぼくたち；Bokutachi」and 「俺たち；おれたち；Oretachi」.
「私；わたし；Watashi」: when and how it is used
「私；わたし；Watashi」is likely to be the most common word used to mean “I”. Unlike the other three words meaning “I”, everyone uses this one.
Example sentences:
Watashi no namae wa Yamaguchi desu.
私の名前は山口です。
わたしのなまえはやまぐちです。
My (sur) name is Yamaguchi.
Watashi wa ongaku wo kiku kotoga suki desu.
私は音楽を聴くことが好きです。
わたしはおんがくをきくことがすきです。
I like listening to music.
Watashi no shorai no yume wa kashu desu.
わたしの将来の夢は歌手です。
わたしのしょうらいのゆめはかしゅです。
My future dream is to be a singer.
Like these example sentences, you use “I” 「私；わたし；Watashi」to talk anything about “me”.
「あたし；Atashi」: When and how it is used
「あたし；Atashi」is an informal spoken word used by female speakers to mean “I” or 「私；わたし；Watashi」. You use 「あたし；Atashi」in conversations among friends to make it more informal.
Example sentences:
Atashi mo suki!
あたしも好き!
あたしもすき！
I like it, too!
Atashi no pen minakatta?
あたしのペン見なかった？
あたしのペンミなかった？
Didn’t you see my pen?
Sore, atashi no!
それあたしの！
That’s mine!
In this way, 「あたし；Atashi」is a conversational word spoken in daily small conversations among families and friends.
「僕；ぼく；Boku」: when and how it is used
「僕；ぼく；Boku」is a word used by children, but only male ones. At times, adult males can use it but it sounds childish and informal. It’s important to note that especially for those using 「僕；ぼく；Boku」, as they are very young in age, they don’t normally use kanji, 「僕」but only use hiragana「ぼく」in written contexts. 「僕」as used in kanji is often used by grown-up teenagers or more likely, adults.
Example sentences:
Boku no yume wa Uchuu hikoushi ni narukoto desu.
僕の夢は宇宙飛行士になることです。
ぼくのゆめはうちゅうひこうしになることです。
My dream is to be an astronaut.
Boku wa nana sai desu.
僕は七才です。
ぼくはななさいです。
I am 7 years old.
Boku tachi wa itsumo issho datta.
僕たちはいつも一緒だった。
ぼくたちはいつもいっしょだった。
We were always together.
「俺；おれ；Ore」：when and how it is used
「俺；おれ；Ore」is an informal word to mean “I” and used by male speakers in conversations with those they are close. You may see this word used in anime and manga to show aggressiveness of the person using it, but in daily conversations, 「俺；おれ；Ore」is perfectly fine to use in any contacts among friends and those in close relationships.
Example sentences:
Kore wa ore no pen da.
これは俺のペンだ。
これはおれのペンだ。
This is my pen.
Oretachi wa sakini kaeru.
俺たちは先に帰る。
おれたちはさきにかえる。
We come home first.
Ore no sukina youni sasete kure.
俺の好きなようにさせてくれ。
おれのすきなようにさせてくれ。
Leave it to me.
It is interesting to see that when you use 「俺；おれ；Ore」, as it is used by male speakers, forms of language change in ways male speakers express.
Conclusion
While 「私；わたし；Watashi」is the word used to mean “I”, it is useful to use other words as Japanese people use them in daily spoken conversations and also messages. For adult Japanese learners, 「あたし；Atashi」and 「俺；おれ；Ore」are very useful in conversations with Japanese friends or colleagues and usage will show your further approach to Japanese culture.
Chisaki Yamaguchi