die Linie
line
A long, narrow mark on a surface.
Bitte unterschreiben Sie auf der gepunkteten Linie.
Please sign on the dotted line.

line
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line
A long, narrow mark on a surface.
Bitte unterschreiben Sie auf der gepunkteten Linie.
Please sign on the dotted line.

The expression 'in erster Linie' (primarily/first and foremost) is a fixed expression and means 'mainly' or 'above all.' It often appears at the beginning or in the middle of a sentence to emphasize what is most important.
Mir geht es in erster Linie darum, dass alle zufrieden sind.
What matters to me primarily is that everyone is satisfied.
In connection with public transportation, 'Linie' (line) is used whenever a specific route is meant. For example, you say 'die Linie 5 nehmen' (to take line 5) or 'mit der Linie 10 fahren' (to travel on line 10).
Welche Linie fährt zum Hauptbahnhof?
Which line goes to the main train station?
When 'Linie' (line/approach) describes a strategy or attitude, it is often combined with verbs like 'verfolgen' (to pursue), 'fahren' (to take/pursue), or 'vertreten' (to represent/advocate). The expression 'seiner Linie treu bleiben' (to stay true to one's line) is also common.
Das Unternehmen verfolgt eine klare Linie bei der Produktentwicklung.
The company is pursuing a clear line in product development.
When talking about telephoning, 'die Linie' (the line) can mean the connection. Typical phrases are 'die Linie ist besetzt' (the line is busy) or 'jemanden in der Linie haben' (to have someone on the line).
Ich habe versucht anzurufen, aber die Linie war ständig besetzt.
I tried to call, but the line was constantly busy.
In connection with appearance, 'Linie' (figure/outline) describes the body shape. A typical expression is 'auf seine Linie achten' (to watch one's figure), which means to pay attention to one's weight or figure.
Er isst viel Gemüse, weil er auf seine Linie achtet.
He eats a lot of vegetables because he watches his figure.
When it comes to family relationships, 'Linie' (line/lineage) is used to describe ancestry. The fixed expression is often 'in direkter Linie' (in a direct line) or 'in weiblicher/männlicher Linie' (through the female/male line).
Die Familie kann ihre Vorfahren in direkter Linie bis ins 17. Jahrhundert zurückverfolgen.
The family can trace its ancestors in a direct line back to the 17th century.
In the basic meaning of a stroke or mark, 'Linie' (line) is often used with verbs like 'ziehen' (to draw), 'zeichnen' (to draw), or 'malen' (to paint/draw).
Der Architekt zog mit dem Bleistift eine gerade Linie auf dem Plan.
The architect drew a straight line on the plan with a pencil.
politics / policy
'die Politik' and 'die Linie' can both mean a basic approach or strategy. In this sense, they are about how a person, company, or group wants to achieve its goals. 'Politik' often sounds more formal and can mean the rules or principles of an organization, for example 'eine Personalpolitik' (a personnel policy). 'Linie' puts more emphasis on the clear direction or stance that someone follows. The words can be confused when talking about strategies. 'Politik' is more suitable for fixed rules and measures, while 'Linie' is more suitable for a stance or direction in decisions.

Im Gespräch blieb die Chefin bei ihrer klaren Linie.
In the conversation, the boss stuck to her clear line.
Die Firma ändert ihre Politik und erlaubt jetzt mehr Arbeit von zu Hause.
The company is changing its policy and now allows more work from home.