What is meant by "residual"?

The term "residual" refers to something that remains after the majority of something has been removed, used, or dealt with. Specifically, it denotes what is left over or what remains in a particular context. For example, in mathematics, residuals are the differences between observed and predicted values, signifying what is left after accounting for the modeled values. In various fields, including finance and science, residuals indicate what persists after significant transactions or processes.

The other choices do not align with this definition. A part that is newly created implies something that has not existed before, which contrasts with the idea of leftover components. A temporary solution suggests a fix that is not permanent, lacking the aspect of something remaining after an original element has been addressed. Lastly, a main component denotes a primary or essential part, which does not capture the essence of something being leftover. Thus, the concept of "residual" is most accurately represented by the notion of describing a part left over.