"Well, that was a waste!" is a term that is emphatic, really drawing attention to the wastefulness that has taken place and how disappointing it was. This term is given a more emphatic touch with the additional word, "well", which in English is used at times to add a degree of emphasis. It also can be said in a sarcastic manner.
"That was a waste of energy." is another statement that means the same, however, it doesn't have the power the previous statement does nor is it said in any particular way. It simply denotes that energy has been wasted unnecessarily on an endeavor.
"Well, that was a waste!"（本当に無駄だったよ）
語気の強い言い方です。無駄だったこと、ガッカリした気持ちを表します。
この表現は「well」によってさらに強い言い方になっています、時々このような使い方をします。また、皮肉っぽく言うこともできます。
"That was a waste of energy."（無駄な努力だった）
これも意味は同じです。ただ、一つ目ほど強くありません、普通の言い方です。単に、努力がエネルギーの無駄だったと表します。
What a waste of time. - You can say this when you don't think whatever you did was worth your time or effort. Often said when you are annoyed that something took especially long or you didn't enjoy what you were doing.
That was way more effort than it was worth. - This is said when you expended more energy and effort than was worth whatever the outcome was of your task. A sentence example is "I hate taking crab out of their shell, its way more effort than they are worth".
Well, that was definitely not worth my while! - "Worth my while" is an idiom used when the outcome of your task was not worth the effort you expended. You can also use it in a positive light, an example being "I love finding good sales at the market! Its always worth my while".
What a waste of time.
〔訳〕時間の無駄もいいとこ。
時間、努力の無駄だったと表す言い方です。時間がかかってイライラしたときや、つまらなかったときに、よく使います。
That was way more effort than it was worth.
〔訳〕努力の無駄だった。
労力のわりに成果が得られなかったときに使います。
例：
"I hate taking crab out of their shell, it's way more effort than they are worth".
〔訳〕カニの殻をむくのが嫌い。努力の無駄だ。
Well, that was definitely not worth my while!
〔訳〕全く時間の無駄だった！
「worth my while（＝イディオム）」は、努力のわりに成果が得られなかったことを表します。肯定的に使うこともできます：
"I love finding good sales at the market! It's always worth my while".
〔訳〕マーケットで掘り出し物を見つけるのが好きです。無駄になることはないよ。
I'll never get those (insert time period) back, what a waste!
These are three ways you can express that your effort was wasted. In the third sentence you will see a common sentence we use if we feel like we have wasted time or effort on someone or something. Lets say for example you spent the whole weekend working on a project. On Monday when you present your project your boss informs you that they are going to try something else. You probably will say to yourself 'I'll never get those two days back, what a waste!'.
三例とも、努力が無駄だったと表す言い方です。
三つ目の例は、時間、努力を無駄にしたときによく使います。例えば、あなたは週末丸々ある企画に費やしました。月曜日、上司に提出すると「別のことをやってみる」と言われます。あなたは心の中でつぶやくでしょう：
'I'll never get those two days back, what a waste!'
〔訳〕あの2日は戻ってこない。本当に無駄だった！
You may also say to someone who has spent time or effort doing something without reward as being 'a fool's errand.'
EX
A: "Why have you been digging a hole in the ground all day? You must be exhausted!"
B: "I have been looking for a water pipe. But I've had no luck at all! I think it has been a waste of time.."
A "Yes, it seems to have been a fool's errand, I'm afraid.'
報酬がないのに時間を費やしていたり、または努力してる人に対して骨折り損（a fool's errand）してるとして下記のように言えるでしょう。
例：
A: Why have you been digging a hole in the ground all day? You must be exhausted!
何故、一日中地面に穴を掘っているんだ？あなたは、疲れ果ててるにちがいない！
B: I have been looking for a water pipe. But I've had no luck at all! I think it has been a waste of time.
水道管を見つけていたんだよ。でも、全然運がなかった！無駄な時間だったよ。
A: Yes, it seems to have been a fool's errand, I'm afraid.
そうだね、残念だけど、むだ足だったようだね。
You could say 'Well that was a waste of time/energy', meaning the time you spend doing something did not give you the result you wanted. You could also say that something was pointless meaning it had no point as the end goal was not reached.
「Well that was a waste of time/energy.」と言えます。
この意味は、何かするのに時間を費やしたけれども求めていた結果が得られたかったということです。
「that was pointless」も使えますが、最終目標に達しなかったため無意味だったという意味です。
If you do something that and it didn't work out the way ot should have then it's called 'wasted effort' it can also be called 'a waste of energy' meaning you used your energy for no reason as it didn't work out this can also be called 'a waste of time' meaning to waste your time doing it
何かをして思うような結果にならなかったなら、それは'wasted effort'（無駄になった努力）と表せます。
他に、'a waste of energy'（労力の無駄）と言うこともできます。無駄なことに労力を使ったという意味です。
'a waste of time'（時間の無駄）と言うこともできます。時間を無駄にしたという意味です。
Worthless＝「価値がない」
Waste＝「無駄」
A waste of time＝「時間の無駄」
Forget about it. It’s worthless and a waste of time.
「そんなことしなくていいよ。価値がないし時間の無駄だ」
Forget about it.は直訳で「そのことは忘れろ」と、そのままの意味で使われることもありますが、「そんなことしなくていいよ」という場面でも使われます。
ご参考まで
英会話講師のKOGACHIです(^^)/
「無駄な努力だよ」は、1つには
You're wasting your energy.
「あなたは自分のエネルギーを無駄にしている」
と表現できます。
以上ですm(_)m
少しでも参考になれば幸いです(#^^#)
お困りの時は、いつでも気軽にご質問ください(^0^)/
★★どうぞよろしくお願いもうしあげます★★
see you soon♪
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