If you are planning on having a speech and you need to mention about 3 different reasons for a topic that you are talking about, there are a couple different ways you could say this:
1) There are three reasons for this.
2) Here are three reasons why _________.
3) There are three reasons.
スピーチの中で三つの[理由](https://eikaiwa.dmm.com/uknow/questions/51867/)を挙げるなら、いくつか言い方があります：
1) There are three reasons for this.
（これには三つ理由があります）
2) Here are three reasons why _________.
（_________の三つの理由です）
3) There are three reasons.
（三つ理由があります）
If you are making a speech and you have three reason for or against a certain topic.
Example:
Here are three reasons why drinking water is good for your health.
Here are three reasons why eating fast food is not good for your health.
If you are discussing a certain topic and there are three reasons in particular that you want people to focus on.
Example:
The software trial was not successful. There are three main reasons for this. Reason number 1 is that ______ , reason number two is because _____ and the third reason is because ____.
スピーチで、あるテーマについて肯定的または否定的な理由を三つ挙げる場合：
例:
Here are three reasons why drinking water is good for your health.
（水を飲むことが健康にいい理由は三つあります）
Here are three reasons why eating fast food is not good for your health.
（ファーストフードが健康に良くない理由は三つあります）
あるテーマについてディスカッションしていて、三つの理由を示したい場合は：
例:
The software trial was not successful. There are three main reasons for this. Reason number 1 is that ______ , reason number two is because _____ and the third reason is because ____.
（ソフトウェアトライアルではありませんでした。これには[三つ理由があります](https://eikaiwa.dmm.com/uknow/questions/37280/)。[一つ目は](https://eikaiwa.dmm.com/uknow/questions/65362/)_____、二つ目は_____、三つ目は_____）
Eg. "I wish to study in Canada for three reasons."
Eg "There are 3 compelling reasons why I want to study in Canada."
Above are two different ways to arrange your statement. You may use the adjective 'compelling' to underline your points.In speech-making 'three' is considered the ideal number of points to convey your argument.
例：
"I wish to study in Canada for three reasons."
3つの理由でカナダで勉強したい。
"There are 3 compelling reasons why I want to study in Canada."
わたしがなぜカナダで勉強したいか3つの切実な理由があります。
これらは、あなたの言いたいことを伝える2つの別の表現です。ポイントを強調するために、形容詞 'compelling'を使うことができます。
スピーチを作るには、「3」はあなたの意見を述べる理想的な数字とされています。
During a speech you may wish to use a phrase such as this to point out to the audience what you intend to tell them. If there are more than three reasons or causes but you are only intending on focussing on a few you could add the words 'main' or 'pertinent' .
'We discovered three main causes'
'Let's discuss three pertinent reasons'
As your speech develops, you could say
'The first reason is ...'
'Moving on to the second cause ....'
'And my final point to make today is ....
スピーチなどの際には、このようなフレーズが使いたくなるかもしれません。
もし理由・原因が四つ以上あって、その中のいくつかに焦点を当てたいと言うことなら、'main'（主な）や'pertinent'（関係する）という言葉を加えることができます。
'We discovered three main causes'（私たちは主な原因を三つ見つけました）
'Let's discuss three pertinent reasons'（三つの関連する理由について話しましょう）
スピーチが展開する中で、以下のフレーズが使えます。
'The first reason is ...'（一つ目の理由は....）
'Moving on to the second cause ....'（二つ目の原因ですが....）
'And my final point to make today is ....（そして、最後に....）
When saying a speech if there are 3 reasons you want to explain you would say 'There are 3 reasons for this' if you wanted to explain what they are you would say 'There are 3 reasons why'
If there are more than 3 reasons but you want to explain the main 3 you would say 'There are 3 main reasons for this or 'the 3 main reasons are'
3つの理由を述べるときは、”There are 3 reasons for this."（これには3つの理由があります）または、”There are 3 reasons why"（3つの理由があります）と言います。
もし3つ以上の理由があり、主に3つの理由を挙げるとしたら、”There are 3 main reasons for this"（これには主に3つの理由があります）または、”The 3 main reasons are..."（主な3つの理由は…）と言います。
When you are giving a speech and want to explain that there are three reasons for whatever it is you are saying; then you may say this in the following ways:
-There are three reasons for this...
-The three reasons for this are (as follows)...
For example:
-There are three reasons for people not succeeding in their work. Firstly, people fail to plan. Secondly, poor time management results in poor work product. Thirdly, people often don't know how to work smart/efficiently.
スピーチで何かについて、三つの理由があると言いたいときは、以下のフレーズが使えます。
-There are three reasons for this...
これには、三つの理由があります。
-The three reasons for this are (as follows)...
この三つの理由は（次の通りです）
例：
-There are three reasons for people not succeeding in their work. Firstly, people fail to plan. Secondly, poor time management results in poor work product. Thirdly, people often don't know how to work smart/efficiently.
仕事で成功しない人には三つの理由があります。まず、計画できないことです。次に、タイムマネジメントができないと成果は上がりません。三つ目に、スマートな/効率のよい働き方を知らない人が多いです。
Reasons are explanations or causes that happen due to an event or a situation. For example "The main reason I am here, is to support my husband".
There are reasons for almost everything we do in life (reason we work is to make money).
"reason"（理由）とは、状況や出来事を引き起こす原因（cause）や説明（explanation）のことです。例えば：
"The main reason I am here, is to support my husband".
（私がここにいる一番の理由は、主人をサポートするためです。）
私たちのすることのほぼすべてに"reason"（理由）があります（働く理由はお金を稼ぐことです）。
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