When talking about jobs, roles, or acting in a certain capacity, English uses "as" (e.g., "I work as a consultant"). Russian has two main ways to express this: using как or the phrase в качестве.
Using как (as)
When using как to express someone's role, the job title must match the case of the person being described. Most often, you are describing the sentence's subject, so the role stays in the Nominative case.
| Anna works here as an intern. | Анна работает здесь как стажёр. |
| I am helping them as a consultant. | Я помогаю им как консультант. |
| The grandmother helps us as a nanny. | Бабушка помогает нам как няня. |
Using в качестве (in the capacity of)
The phrase в качестве literally translates to "in the quality of." It is slightly more formal and very common in professional contexts.
| as / in the capacity of | в качестве |
Unlike как, в качестве acts like a preposition and is always followed by the Genitive case.
| He works at the company as an assistant. | Он работает в компании в качестве ассистента. |
| She works for us as a nanny. | Она работает у нас в качестве няни. |
Even if the person being described is the direct object (like "him" in the Accusative case below), the role still takes the Genitive case:
| We hired him as an intern. | Мы наняли его в качестве стажёра. |
Substituting and Replacing
When someone acts in a role temporarily, use the verb заменять (imperfective) or заменить (perfective) to express substituting or replacing. These verbs take a direct object in the Accusative case.
| I often substitute for the manager. | Я часто заменяю менеджера. |
| Can you substitute for the consultant tomorrow? | Ты можешь заменить консультанта завтра? |