Explanation
Use "be going to" for a plan or a future result that is clearly understood now. Use "will" for a decision made now, a promise, an offer, or a prediction based on what you think.
For example, "I'm going to study tonight." Here, "I'm" means "I am," and "going to" shows a plan already decided before speaking. "study" is the main verb, and "tonight" gives the time. Japanese often uses one future form, like "〜するつもりです" or "〜します," but English often chooses between "will" and "be going to."
予定が前から決まっているときや、もう見えている未来には "be going to" を使います。今その場で決めたこと、約束、申し出、または自分の考えによる予測には "will" を使います。
たとえば "I'm going to study tonight." では、"I'm" は "I am" の短縮形で、"going to" が「前からある予定」を表します。"study" が本動詞で、"tonight" が時間を表します。日本語では「〜するつもりです」「〜します」のように1つの形で言えますが、英語では "will" と "be going to" を使い分けます。
Examples
- I'm going to study tonight. 今夜は勉強するつもりです。
- She's going to visit her grandmother tomorrow. 彼女は明日、おばあさんを訪ねる予定です。
- Are you going to stay here? ここにいるつもりですか。
- We won't be late. 私たちは遅れません。
- I think it will rain later. あとで雨が降ると思います。
- The dark clouds mean it's going to rain soon. 黒い雲が出ているので、もうすぐ雨が降りそうです。
Common Mistakes
Japanese learners often use "will" for a plan that was already decided.
Wrong: "I will meet my friend after work."
Right: "I'm going to meet my friend after work."
If the plan already exists, "be going to" is usually better.
日本語では未来の予定をそのまま言えるので、前から決まっている予定にも "will" を使ってしまいがちです。
誤り: "I will meet my friend after work."
正しくは: "I'm going to meet my friend after work."
予定がすでに決まっているなら、ふつうは "be going to" を使います。