Two vertical strokes side by side, stating that two lines never meet.
Also known as: Two vertical lines
∥ states that two lines are parallel. The same pair of strokes is used in several other roles — the norm of a vector, absolute value, concatenation in some languages — so the context does the work.
Is encoded as U+2225 PARALLEL TO in the Mathematical Operators block.
Contexts: Mathematics
States that two lines or planes are parallel, never meeting however far they are extended.
Contexts: Mathematics
Shares its shape with several unrelated notations — the norm of a vector, a doubled absolute-value bar, and string concatenation in some languages — so the surrounding expression rather than the character carries the meaning.
Contexts: Mathematics
Two straight vertical strokes of equal length standing side by side with a narrow even gap between them.
Lines that never meet, against lines meeting at a right angle.