Abstract: This article analyzes the instances of using short and long forms of the adjectives the Old Slavonic language, as well as the analytical method of expressing the category of certainty / uncertainty in the Slovene language of the XVI century based on the example of translations of the fragments from the New Testament. The comparison of short and long forms of the adjectives is one of the ways of conveying the category of certainty / uncertainty in the Slavonic language without articles. A similar comparison of short and long forms of the adjectives can be observed in both Old Slavonic and Old Slovene languages. However, in the Slovene language, such juxtaposition ceased to exists as a result of the early contraction in pronominal forms of the adjectives; the XVI century marks the formation of the analytical method of conveying the category certainty / uncertainty using the article “ta” and “en”. The following conclusions were made: the original language could affect the translation strategy and the choice of forms, while in the Slovene language it also pertained to articles; the examples of Slovene translations that preserved the correlation of short and long forms without the presence of the part or article in the originals, testify to the development of special ways of expressing the category of certainty / uncertainty, which replaced the juxtaposition of short and long forms of the adjectives; the analytical forms in the Slovene corresponded with short and long forms of the adjectives in the Old Slavonic language, which emphasizes the similar functional yield of analytical forms with the previous juxtaposition of short and long forms of the adjectives in the Slovene language.