Here's why and some alternatives depending on the context:
* Capacity is a noun, describing the ability to hold or contain something.
* Adverbs modify verbs, adjectives, or other adverbs, describing how, when, where, or to what extent something is done.
Here are some options for expressing the idea of "capacity" with adverbs:
To express the *extent* of capacity:
* Fully: The room was fully occupied.
* Partially: The tank was only partially filled.
* Maximally: The engine was operating maximally.
* Adequately: The storage space was adequately sized.
To express the *manner* of capacity:
* Efficiently: The system operates efficiently, using minimal resources.
* Effectively: The program was designed to effectively manage large amounts of data.
* Successfully: The company successfully met its production capacity.
To express the *time* of capacity:
* Currently: The factory is currently operating at full capacity.
* Previously: The building previously had a capacity of 100 people.
* Consistently: The team has consistently exceeded their capacity.
To express the *comparison* of capacity:
* More: The new model has a more spacious interior.
* Less: The smaller version has less storage capacity.
* Equally: Both options have equally powerful engines.
The best adverb depends on what you want to emphasize.