ydintä

Ydintä is the partitive singular form of the Finnish noun ydin, which means nucleus or core. The word has two principal senses in scientific contexts: in biology, the cell nucleus; in physics, the atomic nucleus at the center of an atom. In Finnish, ydintä is used when the nucleus is the object of a verb or described in a partitive construction, for example: Tutkin ydintä mikroskoopilla (I am studying the nucleus with a microscope) or Kalvo ympäröi ydintä (The membrane surrounds the nucleus).

In biology, the cell nucleus is the organelle that contains the cell’s DNA and regulates gene expression. It is bounded by the nuclear envelope and plays a central role in processes such as transcription and replication. In physics, the atomic nucleus consists of protons and neutrons and is held together by the strong nuclear force; it determines the atom’s identity and properties, including isotopes and nuclear reactions. The common Finnish terms for these concepts are solun ydin (cell nucleus) and atomiydin (atomic nucleus).

Beyond science, ydin can also mean the core or essence of a matter. For example, the expression kysymyksen ydin refers to the central point of a question. In such metaphorical uses, ydin denotes what is most important or central in a discussion or problem.

Etymology and usage notes: ydin is a native Finnish word and forms compounds naturally, such as atomiydin, ydinsäteily (nuclear radiation), and ydinvoima (nuclear power). The form ydintä is strictly grammatical, signaling partitive case rather than introducing a distinct concept.