Inertial inflation is a situation in which all prices in an economy are continuously adjusted with relation to a price index by force of contracts.
Contracts are made to accommodate the price-changing scenario by means of indexation.
Indexation in a high-inflation economy is evident when, for instance, a given price must be recalculated later to incorporate inflation accumulated over the period to "correct" the price.
In the medium and long terms, economic agents begin to forecast inflation and to use those forecasts as de facto price indexes that can trigger price adjustments before the actual price indices are made known to the public.
At worst, inflation tends to grow exponentially and leads to hyperinflation.