American or America?

By the third generation, the original language is lost in the majority of immigrant families. Hence the description of America as a “graveyard” for language.

等于：

By the third generation, the original language is lost in the majority of immigrant families. Hence comes the description of America as a “graveyard” for language.

hence从句中，常省略谓语动词result或者come。hence前的标点符号，可能是破折号，逗号，点号后另起一句，也可能是分号。

1. The meter bridge is usually one meter long---hence the name.

米桥通常长1米，因此得名。

2. Proteins are essential to the growth and the rebuilding of body tissues, hence their importance.

蛋白质对于人体组织的生长和修复是至关重要的，因此它们非常的重要。

3. Different emf’s result in potential gradients. Hence electric fields.

4. The transistor has its materials arranged p-n-p, hence the name pnp transistor.

=The transistor has its materials arranged p-n-p, hence comes/results the name pnp transistor.

该晶体管把它的材料排列成p-n-p形式，因而得到了pnp晶体管这一名称。