这些岩层被称作地层（strata）（stratum的复数形式）， 单个岩层称为stratum。

These layers are called strata and a single layer is called a stratum.

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数学家对此很熟悉；如果将代数中的常见问题考虑成复数而不是实数时，那么这些问题就更容易处理，尽管复数算法较难。

Mathematicians are familiar with this; common problems in algebra are more tractable when considered over the complex numbers than over the reals, even though complex arithmetic is more difficult.

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这也是为什么，从FORTRAN开始，复数是这些语言的标准。

This is why it was standard in languages dating back to FORTRAN.

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