Viidesosan

Viidesosan is the Finnish term for one fifth of a whole. It denotes a fraction equal to 1/5 and is used both in mathematics and in everyday language whenever a quantity is divided into five equal parts. In decimal form, a viidesosan is 0.2, and it corresponds to 20 percent.

In practical terms, a viidesosan appears whenever something is split into five equal portions. For example, if a cake is divided into five equal pieces, one piece represents a viidesosan of the cake. As a mathematical object, it is a proper fraction with denominator 5, and it is irreducible because 1 and 5 have no common divisors greater than 1.

Finnish fraction naming commonly uses the -osa suffix pattern, with viidesosa being the standard nominative form for one fifth. The term is taught in basic arithmetic and appears in everyday language when discussing portions, proportions, or sharing. The concept also integrates into rules for fractions, such as adding or comparing fractions with the same denominator, where 1/5 serves as a basic unit of measure for fifths.

Historically and linguistically, viidesosan is part of a broader system that names fractions by their denominator, alongside others like neljäsosa (1/4) and kymmenesosa (1/10). While usage may vary with context and inflection, viidesosan remains the common reference to one fifth of a whole.