Start from scratch 意思是从头开始，这是一个口语表达。它可以用来形容一件事情完全从零开始，从起跑线开始。另一个常听到的表达是 build from scratch，意思和前者几乎一样。

例句

Let's start from scratch and see how quickly we can get the food on the table.

让我们从零开始做起，看看我们几时能把菜做好端上桌子。

After their proposal was rejected, the team decided to throw away the plan and start from scratch.

当他们的建议被否定了以后，团队决定完全放弃以前的计划，重新从起跑线开始。

Sometimes it's best to start from scratch, rather than trying to make changes to the existing plan.

有时候最好从零开始，而非根据现成的设计进行修改。

He built his company from scratch and now it's a multimillion pound business.

他白手起家创建了公司，现在这家企业已价值数百万英镑。