Learn German: Der Vorstand lobt die Synergie zweier Abteilungen. - The board praises the synergy of two departments.

Zweier is the genitive form of the number zwei. When a plural noun phrase in the genitive case lacks an article or an adjective to clearly show the case, the numbers zwei and drei take the ending -er. Here, it indicates possession or association, translating to 'of two'.

Would it be wrong to say von zwei Abteilungen instead?

Not at all! Using von plus the dative case (von zwei Abteilungen) is grammatically correct and very common, especially in everyday speech. However, the genitive zweier sounds more formal and professional, which fits perfectly with the corporate context of a board (der Vorstand) making a statement.

Does Vorstand refer to one person or the whole committee?

It can be either. Der Vorstand is a collective noun referring to the entire board of directors or executive committee, which is why it takes the singular verb lobt. However, in everyday business German, it is also frequently used to refer to an individual board member or the CEO.

Why doesn't Abteilungen have a special genitive ending?