In Finnish, you can turn a verb into a physical tool or instrument by adding the suffix -in to the verb stem.
For example, kytkeä (to connect) becomes kytkin (a switch), and katkaista (to cut or break) becomes katkaisin (a light switch).
The -ime- Stem
For most case endings, such as plurals or location cases, the -in ending changes to the stem -ime-.
Other common household appliances formed this way include tuuletin (a fan, from tuulettaa) and lämmitin (a heater, from lämmittää).
The Partitive Exception: -inta / -intä
The partitive case does not use the -ime- stem. Instead, attach -ta or -tä directly to the basic nominative form, resulting in -inta or -intä.
Everyday Gadgets
This pattern applies to a huge variety of objects. Soittaa (to play music) gives us soitin (a musical instrument), and vatkata (to whip) gives us vatkain (a mixer).
Notice that cases using the -ime- stem often trigger the strong consonant grade. For example, the genitive of suodatin (a filter) is suodattimen.
You will also see this suffix in technical and beauty gadgets, like ilmaisin (a detector), kiharrin (a curling iron), and teroitin (a sharpener).