Drop off and Narrow down

Drop off verb - To grow less in scope or intensity especially gradually.

Narrow down and drop off are semantically related In some cases you can use "Narrow down" instead a verb "Drop off".

Narrow down verb - To reduce in size or volume by or as if by pressing parts or members together.

Drop off and narrow down are semantically related in decrease topic. Sometimes you can use "Drop off" instead a verb "Narrow down", if it concerns topics such as grow less or make less.