Downfall and Falloff

Downfall noun - A change to a lower state or level.

Falloff and downfall are semantically related In some cases you can use "Falloff" instead a noun "Downfall".

Falloff noun - The amount by which something is lessened.

Downfall and falloff are semantically related in decline topic. Sometimes you can use "Downfall" instead a noun "Falloff", if it concerns topics such as decrease.