Since summer 2019 there is a new document that defines what in science should be regarded as being one second, one meter, and one kilogram, respectively. It is the ninth edition of the SI Brochure. Compared with older editions, a new definitional approach has been used. The seven base units are now defined by being directly related to a so-called defining constant. The paper discusses the second, the meter, and the kilogram. One odd salient, but nonetheless not discussed, feature of the formulations of the definitions is that, from a purely linguistic point of view, they are circular. That is, symbols for what is to be defined appear also in the defining expressions. However, underneath the circularities there are, appearances notwithstanding, substantially non-circular definitions. The aim of the paper is to uncover these never before presented definitional structures. It is made by means of the two notions absolutely discrete quantities (counts) and metrical coordinative definitions. When the true definitional structures become visible, two important substantial metrological facts can be seen. First, the new definition of the kilogram is very much in need of further discussion. Second, contrary to what the Brochure hints at, there is no need to try to exchange the atomic parameter used in the definition of the second.

自 2019 年夏季以来，有一份新文件分别定义了科学中应将什么视为一秒、一米和一公斤。这是 SI 手册的第九版。与旧版本相比，使用了新的定义方法。现在通过与所谓的定义常数直接相关来定义七个基本单位。论文讨论了秒、米和公斤。定义的表述的一个奇怪的突出特点是，从纯语言学的角度来看，它们是循环的。也就是说，要定义的符号也出现在定义表达式中。然而，在圆形之下，尽管有外观，但基本上是非圆形的定义。本文的目的是揭示这些以前从未出现过的定义结构。它是由两个概念构成的绝对离散量（计数）和度量坐标定义。当真正的定义结构变得可见时，可以看到两个重要的实质性计量事实。首先，千克的新定义非常需要进一步讨论。其次，与手册所暗示的相反，没有必要尝试交换第二个定义中使用的原子参数。