Explanation
"Many" goes with plural countable nouns, like "books," "friends," and "emails." "Much" goes with uncountable nouns, like "time," "milk," and "water."
Look at the sentence "There isn't much milk left." "There isn't" makes the sentence negative, "much" shows a large amount, and "milk" is uncountable, so we use "much." In Japanese, you can say "あまり" for this idea, but English must also choose the right noun type. Use "many" for things you can count one by one, and use "much" for things you do not count one by one.
"many" は複数の可算名詞と一緒に使います。たとえば "books"、"friends"、"emails" です。"much" は不可算名詞と一緒に使います。たとえば "time"、"milk"、"water" です。
"There isn't much milk left." という文を見てみましょう。"There isn't" で否定を作り、"much" で量の多さではなく「たくさんあること」を表し、"milk" は不可算名詞なので "much" を使います。日本語では「牛乳はあまり残っていません」と言えますが、英語では名詞が数えられるかどうかで "much" と "many" を分けます。
Examples
- I don't have much time. 私はあまり時間がありません。
- Do you have many friends? 友だちはたくさんいますか。
- There isn't much milk left. 牛乳はあまり残っていません。
- She has many books in her room. 彼女の部屋には本がたくさんあります。
- How many emails did you get today? 今日、メールを何通受け取りましたか。
- We didn't eat much dinner. 私たちは夕食をあまり食べませんでした。
Common Mistakes
Japanese learners often use "much" with plural countable nouns, or "many" with uncountable nouns, because "たくさん" works for both in Japanese.
Wrong: "I have much books."
Right: "I have many books."
Wrong: "There isn't many water."
Right: "There isn't much water."
日本語では「たくさん」でどちらも言えるため、複数の可算名詞に "much" を使ったり、不可算名詞に "many" を使ったりしやすいです。
誤り: "I have much books."
正しくは "I have many books."
誤り: "There isn't many water."
正しくは "There isn't much water."