radioaktiivisiin

Radioaktiivisiin is a Finnish inflected form of the adjective radioaktiivinen, meaning radioactive. It is the illative plural form, used with plural nouns in the illative case to indicate movement toward or into radioactive objects, substances, or areas. This form reflects how Finnish adjectives agree with the noun in number and case.

In practice, radioaktiivisiin appears in phrases such as radioaktiivisiin aineisiin (into radioactive substances), radioaktiivisiin tiloihin (into radioactive areas), or radioaktiivisiin mittauksiin (toward radioactive measurements). The illative plural ending -isiin signals both plurality and direction, distinguishing it from other forms like radioaktiiviset (nominative plural) or radioaktiivisia (partitive).

The expression is commonly found in technical, safety, and regulatory contexts, where discussions concern handling, accessibility, or containment of radioactive materials, as well as radiation protection and environmental monitoring. In everyday language, speakers may use other case forms or rely on the noun radioaktiivisuus (radioactivity) to convey related meanings without specifying illative direction.

Related terms include radioaktiivisuus (radioactivity), säteily (radiation), and radiologinen suojelu (radiological protection). The word illustrates Finnish grammar’s characteristic noun–adjective agreement and case system, where meaning is shaped by both the adjective’s form and the noun’s grammatical case.