transitional
Describes a temporary state or period of change from one condition to another. Often used in formal or technical contexts.
This system is merely a transitional measure.
過渡的な段階を経て、新しい体制に移行した。
We moved to a new structure after going through a transitional phase.
暫定的 means 'provisional' or 'tentative', often implying a temporary arrangement until something permanent is decided, whereas 過渡的 focuses on the transition itself.
Compound of 過渡 (kato, 'transition') + 的 (-teki, '-like'). 過渡 is itself a compound of 過 (ka, 'pass through') and 渡 (to, 'cross over').