In conversational Russian, the present-tense "to be" is usually dropped entirely (He is an expert = Он эксперт). However, in academic, professional, and formal contexts, you use the verb являться (to be / to serve as).
Whenever you use являться, the noun or adjective phrase that follows it MUST be in the Instrumental case.
| Word Type | Dictionary Form | Instrumental Ending |
|---|
| Masculine Noun | эксперт, лидер | +ом |
| Feminine Noun | истина, иллюзия | -а / -я → -ой / -ей |
| Masculine Adjective | известный, главный | -ый → -ым |
Seeming and Appearances
To express that something "seems" or "appears to be", use the verb казаться. Just like являться, this verb requires the following noun or adjective to take the Instrumental case.
Factors, Signs, and Symbols
These verbs are heavily used when defining abstract or academic concepts, such as identifying a sign (признак) or an important factor (фактор). Notice how the adjectives describing these nouns also take the Instrumental endings.
In the Past Tense
When discussing what things used to be or seemed like in the past, use the past tense forms (казался, казалась, казалось, казались). The verb must agree with the gender and number of the subject, while the object being described remains firmly in the Instrumental case.
