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英文法Grammar · UNIT 01

be動詞（am / is / are）Be-verbs (am / is / are)

「〜です」「〜にいる」を表す文の土台The foundation for “is / am / are” and “there is / are” sentences

基本の説明Overview

英語の文の中でもっとも基本になるのが be動詞 です。日本語の「〜です」「〜にいます・あります」にあたる働きをし、主語のあとに置いて、名詞・形容詞・場所を表す語句をつなぎます。The be-verb is the most basic building block of an English sentence. It links the subject to a noun, an adjective, or a place — covering what Japanese expresses with 〜です and 〜にいる / ある.

be動詞には am / is / are の3つの形があり、主語によって使い分けます。「だれが（何が）」にあたる主語を見て、下の表のどれを使うか決めましょう。The be-verb has three forms — am, is and are — and the subject decides which one to use. Look at the subject, then choose from the table below.

主語Subjectbe動詞Be-verb短縮形Short form
IamI'm
youareyou're
he / she / itishe's / she's / it's
wearewe're
theyarethey're
単数の名詞（Tom, my mother, this bookなど）A singular noun (Tom, my mother, this book…)is—
複数の名詞（my friends, these booksなど）A plural noun (my friends, these books…)are—
主語 + am / is / are + 補語（名詞・形容詞・場所など）Subject + am / is / are + complement (noun, adjective, place, etc.)肯定文の基本の並び方。疑問文は be動詞を主語の前に出し、否定文は be動詞のあとに not を置きます。That's the word order for a statement. For a question, move the be-verb to the front; for a negative, put not right after it.

be動詞には2つの意味があります。①「A は B です」（主語＝補語）、②「〜にいる・ある」（場所）。どちらも be動詞の形は同じルールで決まります。The be-verb has two uses: (1) “A is B” (the subject equals the complement), and (2) “be somewhere” (a place). The form follows the same rule in both.

例文で確認Example sentences

① 「〜です」（肯定文）1. “… is / am / are …” (statements)

I am a junior high school student.
私は中学生です。
You are my best friend.
あなたは私の親友です。
you は相手ひとりのときでも are を使う。Use are with you even when you mean just one person.
He is a teacher.
彼は先生です。
My mother is a nurse.
私の母は看護師です。
名詞が主語でも、単数なら is を使う。A singular noun as the subject takes is.
She is very kind.
彼女はとても親切です。
These books are very interesting.
これらの本はとてもおもしろいです。
複数の名詞が主語なら are。A plural noun as the subject takes are.
It is cold today.
今日は寒いです。
天気・寒暖を言うときの It は「それ」と訳さない。When It describes weather or temperature, it is not translated as “that”.

② 「〜にいる・ある」（場所）2. “be somewhere”

We are in the library now.
私たちは今、図書館にいます。
My cat is under the table.
私のねこはテーブルの下にいます。
The station is near here.
駅はこの近くにあります。
場所の語句（in / under / near など）が補語になる。A place phrase (in / under / near…) works as the complement.

③ 疑問文（〜ですか）3. Questions

Is this your bag?
これはあなたのかばんですか。
be動詞を主語の前に出す。The be-verb moves in front of the subject.
Are you hungry?
あなたはおなかがすいていますか。
Yes, I am. / No, I'm not. のように be動詞で答える。Answer with a be-verb: Yes, I am. / No, I'm not.
Is your father at home?
あなたのお父さんは家にいますか。
Yes, he is. / No, he isn't. で答える。Answer with Yes, he is. / No, he isn't.
Where are you from?
あなたはどこの出身ですか。
疑問詞（where）＋ be動詞 ＋ 主語 の順になる。With a question word: where + be-verb + subject.

④ 否定文（〜ではありません）4. Negatives

He is not busy today.
彼は今日忙しくありません。
is not は isn't と短縮できる。is not can be shortened to isn't.
I am not tired.
私は疲れていません。
am not は I'm not と短縮する（amn't とは言わない）。am not becomes I'm not (we never say amn't).
They are not in the classroom.
彼らは教室にいません。
are not は aren't と短縮できる。are not can be shortened to aren't.
This isn't my umbrella.
これは私のかさではありません。

⑤ 短縮形（会話でよく使う形）5. Short forms (common in conversation)

I'm from Japan.
私は日本の出身です。
I am → I'm。会話や手紙ではこの形がよく使われる。I am → I'm. This form is common in speech and informal writing.
She's a good singer.
彼女は歌が上手です。
We're late for school.
私たちは学校に遅れています。

確認クイズQuick check

空所に am / is / are のどれかを入れましょう（疑問文は文頭の大文字に注意）。Fill in each blank with am, is or are (watch the capital letter at the start of a question).

  1. My sister ___ a college student.
    答えを見るShow the answer
    is — 主語 My sister は単数（she）なので is。My sister is singular (she), so is.
  2. You and I ___ classmates.
    答えを見るShow the answer
    are — You and I は複数（we）なので are。You and I is plural (we), so are.
  3. ___ your parents at home?
    答えを見るShow the answer
    Are — your parents は複数なので Are で始める。your parents is plural, so start with Are.
  4. I ___ not hungry.
    答えを見るShow the answer
    am — 主語が I のときは am。With the subject I, use am.
  5. The students ___ in the gym.
    答えを見るShow the answer
    are — The students は複数なので are。The students is plural, so are.
  6. ___ this your pen?
    答えを見るShow the answer
    Is — this は単数なので Is で始める。this is singular, so start with Is.

おさえておきたいポイントKey points

  • 主語が I なら am、he / she / it・単数名詞なら is、you・we・they・複数名詞なら are を使うUse am with I, is with he / she / it or a singular noun, and are with you / we / they or a plural noun
  • you は相手がひとりでも are を使うAlways use are with you, even for one person
  • 疑問文は be動詞を文の先頭に出すだけでOKTo make a question, simply move the be-verb to the front of the sentence
  • 否定文は be動詞の直後に not を置く（isn't / aren't / I'm not の短縮形も覚える）To make a negative, put not right after the be-verb (learn isn't / aren't / I'm not too)
  • 「〜にいる・ある」も be動詞で表す（場所を表す語句が続く）“Be somewhere” also uses the be-verb, followed by a place phrase
よくある間違いCommon mistake："I is a student." ✗ → "I am a student." ✓ 主語が I のときは必ず am を使います。"I is a student." ✗ → "I am a student." ✓ Always use am when the subject is I.
よくある間違いCommon mistake："Are she a teacher?" ✗ → "Is she a teacher?" ✓ 疑問文でも、主語に合った be動詞を使います。"Are she a teacher?" ✗ → "Is she a teacher?" ✓ In a question too, choose the be-verb that matches the subject.
よくある間違いCommon mistake："He not is busy." ✗ → "He is not busy." ✓ not は be動詞のあとに置きます。"He not is busy." ✗ → "He is not busy." ✓ Put not after the be-verb.