die Faser
fiber
A thin, thread-like structure that can be natural (e.g., in plants or muscles) or artificial (e.g., in textiles).
Der Pullover ist aus einer sehr weichen Faser gemacht.
The sweater is made from a very soft fiber.

fiber
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fiber
A thin, thread-like structure that can be natural (e.g., in plants or muscles) or artificial (e.g., in textiles).
Der Pullover ist aus einer sehr weichen Faser gemacht.
The sweater is made from a very soft fiber.

'Faser' (fiber) is a common component of compound nouns. Examples such as 'Glasfaser' (glass fiber/fiber optic), 'Muskelfaser' (muscle fiber), or 'Naturfaser' (natural fiber) show that it can refer to different kinds of thread-like structures.
Für schnelles Internet wird heute oft ein Glasfaserkabel verlegt.
For fast internet, fiber-optic cable is often laid today.
In the literal sense, 'Faser' (fiber) is often combined with adjectives that describe the material. Common combinations are 'natürliche Fasern' (natural fibers), 'synthetische Fasern' (synthetic fibers), or 'feine Fasern' (fine fibers).
Leinen besteht aus natürlichen Fasern und ist im Sommer sehr angenehm zu tragen.
Linen consists of natural fibers and is very comfortable to wear in summer.
The figurative meaning is almost always used in the fixed expression 'mit jeder Faser' (with every fiber) or 'mit allen Fasern' (with all fibers). It expresses that someone feels or does something with their whole being and very intensely.
Sie ist mit jeder Faser ihres Körpers eine Kämpferin.
She is a fighter with every fiber of her body.
character
'der Charakter' and 'die Faser' can both express something about a person's inner strength or moral attitude. 'Charakter' is the normal and neutral word for a person's qualities. 'Faser' is used figuratively in this sense and usually in the plural, for example when you say that someone is honest or brave 'mit jeder Faser' (with every fiber). This sounds stronger and somewhat more elevated than 'Charakter'. For normal descriptions of a personality, 'Charakter' fits better. 'Fasern' is used more when you want to especially emphasize an inner strength or attitude.

Nach der Arbeit kämpft sie mit jeder Faser dafür, dass ihr Projekt gelingt.
After work, she fights with every fiber of her being to make her project succeed.
Am Telefon merkt man schnell, dass Paul einen offenen Charakter hat.
On the phone, you quickly notice that Paul has an open character.