x-heights. If you make a light weight and the black weight of one typeface, you'll have to make sure that the black weight has a bigger x-height than the light weight (top line drawing). If this is not the case, the black weight will look optically too small when it's combined with the light weight in a line of text.

如果你制作一个包含轻磅（细线体）和重磅（粗黑体）的字体，你应该确保粗黑体的x高度比细线体的略大（见图中上一行）。否则，当粗黑体和细线体在同一行中连排时，粗黑体看上去就要比细线体要小得多。

In display sizes this is not exactly the same. If the type is printed in big sizes there can be a much smaller difference between the x-height of the light and the black weight (bottom line drawing).

但在特排使用中，情况就不太一样。当字体大字号印刷时，两者的x高度之间的差异就微乎其微了（参见图中下一行）。

 

上右：正文字体拥有一致的视觉高度。（而物理尺寸是不一样的）
下右：特排字体的x高度更偏向于物理尺寸上的一致。