die Mittellinie
center line
A line that divides an area, especially a playing field, into two halves.
Der Anstoß beim Fußball erfolgt von der Mittellinie aus.
In soccer, the kick-off takes place from the center line.

center line
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center line
A line that divides an area, especially a playing field, into two halves.
Der Anstoß beim Fußball erfolgt von der Mittellinie aus.
In soccer, the kick-off takes place from the center line.

The word is a simple and logical compound made up of 'die Mitte' (the middle) and 'die Linie' (the line). So it describes a line that is located exactly in the middle of an area.
Der Ball muss beim Anstoß auf der Mittellinie liegen.
The ball must be on the center line for the kick-off.
The context makes the meaning clear. Words like 'Spielfeld' (playing field), 'Sport' (sport), or 'Anstoß' (kick-off) point to the line in sports. Words like 'Straße' (road), 'Verkehr' (traffic), or 'überholen' (to overtake) refer to the marking on a roadway.
Die Spieler stellten sich an der Mittellinie auf.
The players lined up at the center line.
In road traffic, the distinction is important: a 'durchgezogene Mittellinie' (solid center line) must not be crossed, while a 'gestrichelte Mittellinie' (dashed center line) may be crossed.
Da die Mittellinie hier durchgezogen ist, darfst du nicht überholen.
Since the center line is solid here, you are not allowed to overtake.
guideline
'Leitlinie' and 'Mittellinie' can both mean a visible line on a surface or road. The difference lies in the function. A 'Leitlinie' helps you keep to a direction or guides/separates an area. A 'Mittellinie' lies in the middle and divides something into two halves, for example a playing field or a road. The words can be confused because both can appear as markings on the ground. So ask yourself: Does the line only guide movement, or does it mark the middle? Then it is either 'Leitlinie' or 'Mittellinie'.

Nach dem Anstoß lief der Spieler schnell über die Mittellinie.
After the kick-off, the player quickly ran across the center line.
Bei Nebel orientierte sich die Fahrerin an der weißen Leitlinie am Straßenrand.
In the fog, the driver used the white line at the edge of the road for guidance.