Plural of fiftieth; multiple parts when something is divided into 50 equal pieces, or multiple ordinal positions ranked at 50.
From fiftieth (ordinal form of fifty) plus -s (plural). This creates the fractional form 1/50 or describes multiple rank-50 positions.
If you divide a cake into 50 slices, each piece is 1/50 of the cake—a fiftieth—which is getting pretty thin but still visible to the human eye.
Complete word intelligence in one call. Free tier — 50 lookups/day.