Hair only comes in varying degrees of waves, curls and coils or straight.
Do you think it might be the case that these aren't even separate categories but blend into each other? I mean, what is the real difference between and curl and coil? Maybe a curl and a wave I can see. Do waves make a 360? Maybe not, but both curls and coils do, right? I mean, if the difference between curl and coil is something other than size, meaning it varies on some other parameter, might we also expect to find big coils and tiny curls? But when people contrast "curl" and "coil", they generally think of tiny coils and bigger curls.