The phrase "activity waned" is correct and usable in written English.
It can be used to describe a decrease or decline in the level or intensity of an activity over time.
Example: "As the summer ended, outdoor activity waned, and people began to stay indoors more often."
Alternatives: "activity diminished" or "activity declined".
Economic activity waned, and Western Union became a household name.
As our interest in strenuous physical activity waned, a keen interest in Palm Island's cuisine developed.
When and why this activity waned remains to be established, but it is an issue that plays directly to the question of life on the planet.
After the intense phase of activity waned, Montserrat began to rebuild, following an injection of funds from the Department for International Development (DfID), along with the creation of a sustainable development pland, and building of 'temporary' T-1_11 housese in Davy Hill.
After a burst in convective activity overnight, shower and thunderstorm activity waned once more by 0700 UTC.
As the subjects saw more success on the screen, however, activity waned in the areas associated with learning a new task, the researchers found.
All signs are pointing to a long hard winter for the U.S. economy as data pours in that shows business activity waning in light of weak consumer confidence.
All of the RNA species studied, except the 2.0-kb beta-tubulin RNA, decrease between 5 and 19 days in SCE testes, as Sertoli cell mitotic activity wanes, indicating that their levels may be regulated by the developmental signals that influence mitosis.
For now, with international economic activity waning, and hydraulic fracking unlocking oil and gas at an astounding rate, this is a bonus time for the American consumer.
Notwithstanding that development in Fabian theorizing, the society's publishing activities waned in the late 1920s.
As the hours spent teaching non-standardized test activities wane and financial resources disappear, she said, the arts are often flushed to the backwater.
