This is the 113th most frequent Finnish word.
yhden
"Yhden" is the genitive singular form of "yksi," meaning "of one" or "one's" in English.
Here, 'yhden' functions as a quantifier, specifying the number 'one' in the accusative case, tied to 'omena' (apple).
Tarvitsen yhden omenan.
I need one apple.
In this context, 'yhden' again serves as a quantifier indicating a single entity, with 'yksi' being in the accusative form due to the direct object 'kirja' (book).
Valitsin yhden kirjan.
I chose one book.
'Yhden' denotes a quantity of 'one' in the genitive case, associated with 'euro' to indicate possession or value.