is not a good descriptive word when speaking of bees.
How many bees do you see lying on the ground, 20, 30, 40
Bees die on a regular basis. It's part of bee life, short and brutish.
If there are a number of dead bees lying on the ground around the hive one day, sweep them up if you can and wait for the next day and check again. If the bees die every day in seemingly large numbers there is something wrong.
However a few bees lying dead around the hive is usually nothing to worry about on one day.
You may be running out of their natural food, honey. You should, on a warm day open remove the cover and inner cover and pull some frames to actually see what is going on.