The letter in the parenthesis is used if the word ends in a consonant.
Dat. -(e)t -(e)s
Loc. -(i)k -(i)kh
To distinguish between Nominative/Accusative, Partitive/Dative, and Genitive/Locative, the article
or adjective is inflected. If there is no article or adjective, context will tell you what the case is. (For example,
the direct object of a sentence always follows the subject, the partitive will be followed by the plural indefinite article,
indicating "some" or "any", and the locative will have a preposition.)