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| Cardinal : yhdeksän|
Ordinal : yhdeksäs
Adverbial : yhdeksästi
Multiplier : yhdeksänkertainen
Colloquial counting form : ysi
Colloquial ordinal : ykki
|Finnish Wikipedia article on yhdeksän|
From Proto-Finnic *ükteksä. The initial component is yksi (“one”), but the nature of the latter component (shared with kahdeksan (“eight”)) remains disputed. The most common explanation is that it consists of two parts: *e-, the negative verb (ei), and *-ksä, a reflexive verb ending (compare Kalevala forms such as istuikse = istuutuu (“he/she sits (down)”)). The combination would then mean "one is not there", and "of ten" was implied or originally said.
The original nominative yhdeksä was replaced by the genitive form due to seitsen and kymmen (and possibly kahdeksan) ending in -n (which is also the genitive ending), but is attested in older texts, particularly in compounds.
Declension of yhdeksän (type koira)
Declension is the same as type koira (number 10), except of the nominative singular form (*), where an -n is added at the end.