fibra -fib- experimental gismu

x₁ is a fiber of type/material x₂

Also see cilta ("thread").

lensisku

In notes:

bukmapra: x₁ is a quantity of lint (short fluffy fibrous material) of composition x₂
buknailo: x₁ is nylon (type of synthetic polymer) of type/composition x₂.
fibrycmu: x₁=j₁ is the cellulose of fibre x₂=j₂=f₁