High-definition television:

For the commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". When naming a commercial SDTV product, a frame rate can be specified without what?
unanswerable