Final Answer:
A semicentennial anniversary is celebrated after 50 years.
Step-by-step explanation:
To determine the duration celebrated at a semicentennial anniversary, we need to understand the meaning of "semicentennial." The term "semicentennial" refers to a period of 50 years. Therefore, when celebrating a semicentennial anniversary, you are marking the completion of 50 years.
In this context, "semi-" is a prefix meaning half, and "centennial" refers to a period of 100 years. Combining these, a semicentennial is half of a century, or 50 years. So, the final answer is that you celebrate a semicentennial anniversary after 50 years.
This term is commonly used for significant milestones, events, or organizations that have reached the 50-year mark. It's essential to understand such terms to accurately express the duration being referred to in various contexts.