Assume a semantic space demarcated by a set of lexical units occurring in a text. Their transition into word forms is a dynamic semantic process connected with the collocation of the units in text segments. The aim is to find semantic constructs and constituents and to apply Menzerath-Altmann's law, which defines the relationship of language constructs and constituents to the semantic text level. Any text is expected to provide a characteristic arrangement of lexical units in their contextual bonds. This can be explained as a feature of semantic dynamism and possibly also of human thinking. We can metaphorically call it a semantic cataract.