Answer:
The use of the phrasing "a date which will live in infamy" is an example of an application of an aphorism in speechwriting. An aphorism is a short saying that encapsulates a meaning or idea so fully that it can continue to live on in its own right beyond the context of its initial application. FDR's statement falls squarely into this category, having been used in the continual application for many decades since its initial use.
Step-by-step explanation: