If this plan is carried out smoothly, I'm convinced that…
Once this plan is carried out smoothly, I'm convinced that…
What's the difference between those two sentences in meaning? I think it almost sounds the same.
Learn English – the difference between ‘if’ and ‘once’
difference
Best Answer
If the plan is carried out smoothly.....
The conjunction "if" is also used in imaginary and conditional sentences. It's used for saying that one thing can or will happen depending on the happening of something else. So this sentence is conditional.
Once the plan is carried out smoothly.....
This sentence is quite different from the former sentence. It's not conditional. The conjunction "once" in this sentence means "as soon as or when".