Ordinals ending with ⟨-s⟩; consonant gradation in the inflectional stem.
The final ⟨-s⟩ of the nominative is replaced by ⟨-nte-⟩ in the inflectional stem; this is subject to ⟨nt⟩ → ⟨nn⟩ consonant gradation, and becomes ⟨-ns-⟩ before the plural marker ⟨-i-⟩.
Partitive singular ending ⟨-tta⟩/⟨-ttä⟩, replacing the ⟨-s⟩, partitive plural ending ⟨-a⟩/⟨-ä⟩ and genitive plural ending ⟨-en⟩.
In ordinals from 11th to 19th the word -toista is simply added after the forms listed below. See e.g. yhdestoista(“eleventh”)