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Glite Dictionary
principal diagonal

principal diagonal

5.6
A line of numbers in a square table that runs from the top left to the bottom right
  • noun
  • /ˈprɪnsəpəl daɪəˈɡoʊnəl/
  • Specialized
translation icon : diagonal principal
  • The principal diagonal contains all the entries where the row and column indices are equal.

Examples

  • Every identity matrix has ones on its principal diagonal and zeros elsewhere.

  • Adding the elements on the principal diagonal gives you the trace of the matrix.

  • The principal diagonal is essential.

  • Look at the principal diagonal!

  • Adding the elements on the principal diagonal gives you the trace of the matrix.

  • Every identity matrix has ones on its principal diagonal and zeros elsewhere.

  • The principal diagonal consists of all the elements in a square matrix where the row number equals the column number.

Synonyms

main diagonal
vsprincipal diagonal
  • Specialized
5.8

The line of numbers in a square table from the top left to the bottom right

names the same diagonal but uses a different common name

Surface Forms

principal diagonal singular
principal diagonals plural

Morphology

principal + diagonal

The phrase transparently combines 'principal' (main/primary) with 'diagonal' (a line joining nonadjacent corners) to indicate the main diagonal of a square matrix, so a B1 learner who knows both words can infer it refers to the main/primary diagonal (upper-left to lower-right). This compositional pattern is standard in mathematics and appears similarly across many languages, making the meaning predictable from the constituents.

Etymology

Principal diagonal comes from a simple picture: in a square table of numbers the diagonal runs from the top left to the bottom right and principal means 'main'. So the name points to the main line of numbers where the row and the column are the same, which is why it means that special diagonal.