Hallitsevana
Hallitsevana is a Finnish participial form derived from the verb hallita, meaning to govern or rule. In everyday and formal usage it appears as a non-finite form that conveys the sense of acting in a governing capacity. The form can function as part of a larger phrase to indicate that someone is exercising authority in a temporary or transitional role, rather than holding a formal, permanent office.
In practice, hallitsevana is used mainly in historical, political, and legal writing to describe de facto authority
Grammatically, hallitsevana is related to the present active participle hallitseva, with the suffix -na that forms
See also Finnish grammar, participles, acting presidency, and transitional or interim governments.