Each "word" was composed of the "dits" and "dahs" (Morse Code, a dash and a dot both being a "bit" apiece, but with a slightly different duration) needed to indicate one letter of the "word".
For instance, "cow" would require 10 "bits" (dah dit dah dit, dah dah dah, dit dah dah) . "Cows" would require 3 additional "bits" (dit, dit, dit).
Each word, depending on the letters used, would require a different code set and, therefore, a different "bit" set.
<EDIT> Looks like JimB beat me to it. Once again my poor typing skills strike...