Begriffe Faser, Garn, Zwirn

The fiber is the basic building block of textile products.
The fiber is long and thin. It can only be subjected to tensile stress

The yarn is made from many fibers by spinning. The prerequisite for spinning is that the fiber has a certain minimum length of at least 10mm

The thread is created by twisting several yarns together.

Weight numbering yarn thickness and titre

The yarn thickness or titer is given as weight per unit length. This is also referred to as "weight numbering" of the yarns.
In the SI system of units, the meter is the unit for length, the gram is the unit for weight.
The derived unit "tex" (abbreviation Tt) describes the yarn thickness of the fiber in grams/kilometer:

1 tex = 1g/1000m
1 dtex (Dezitex) = 0,1 tex oder 1 Gramm pro 10.000 Meter
1 ktex (Kilotex) = 1.000 tex oder 1 Gramm pro 1 Meter
Das tex ist bei Chemiefasern "Nylon", "Perlon", PA6, PA6.6 und bei Filamenten gebräuchlich

Widely used, but not standard, is the "den", e.g. in women's tights. The den comes from the French "denier".
The den indicates the weight of the yarn per 9000m:

1 den = 1g/9000m

Length numbering fineness and barrel length

The fineness or running length indicates the length per unit of weight.
The unit for the fineness is the "numbering" Nm.
The fineness is indicated for yarns, especially wool yarns.
1Nm = 1m/1g (meter per gram)

In addition to the "numbering" in meters and grams, there is also English and French numbering.
NeB: English numbering for cotton
NeL: English numbering for linen
there is also:
NeK: English numbering for worsted yarn
NeW: English numbering for carded yarn
Nf: French numbering for cotton

The NeL (No. English Linen) is defined as 300 yards per English pound (lb)
1 NeL = 0.604772 Nm

The NeB (No. English cotton) is defined as 840 yards/ per English pound (lb)
1 NeB = 1.6934 Nm

Conversion tex to Nm

Weight numbering: 1 tex = 1g/1000m
Length numbering: 1 Nm = 1m/1g
1 tex = 1000 / Nm
1 Nm = 1000 / tex