Viidesosa

Viidesosa is a Finnish term meaning one fifth of a quantity. It designates a portion equal to 1/5 of a whole; in decimal form it equals 0.2 and in percentage form 20 percent. The word is formed from viides, the ordinal of five, and osa, meaning part or portion, literally the fifth part.

Used primarily in mathematics, statistics and everyday language, viidesosa describes dividing something into five equal parts, with each part representing one viidesosa of the total. For example, if a cake is cut into five equal pieces, each piece is a viidesosa of the cake. It is common in elementary mathematics education to teach fractions using terms like viidesosa, kolmasosa (one third) and neljäsosa (one quarter).

Grammatically, viidesosa is a countable noun. The plural form viidesosat refers to several fifth parts, and it is inflected for cases (e.g., viidesosan in genitive). When written as a fraction, 1/5 is understood as viidesosa in Finnish. The term should not be confused with viides, the ordinal adjective meaning the fifth, used to indicate position rather than a portion.

The concept is used to express proportional parts of a whole and is directly comparable to similar terms in other languages. In educational contexts, it serves as a straightforward way to describe a specific fractional portion and to practice conversion between fractions, decimals and percentages.