How to say "diagonal" in Japanese

• 斜めななめJLPT N2approx.Common
  no-adjective, na-adjectiveThe everyday word for anything that slants, tilts, or slopes rather than running straight — a line, a cut, a path. If you just mean 'at an angle', this is the word you want.
• 対角たいかく
  nounThe geometric term for a diagonal: the line joining opposite corners of a figure, or a point diagonally opposite another. Suited to mathematical and technical description of shapes and positions.
• 斜はすJLPT N2approx.
  no-adjectiveAlso means something slanting or diagonal, but it is less common and you will seldom need it: 斜め does the same job in ordinary language.
• 筋交いすじかい
  no-adjectiveReally a construction term: the diagonal brace set across a frame to stiffen it. Its 'diagonal' is that structural member, so it is not a general word for slanting lines or directions.
• ダイアゴナル
  nounThe loanword from English. It appears mostly in specialist or jargon contexts rather than everyday speech; to say simply that something runs diagonally, 斜め is the word you want.

Choose 「斜め」 for anything slanting, tilted, or diagonal in ordinary use; 対角 for the geometric diagonal between opposite corners; 「筋交い」 for a structural brace; 斜 and 「ダイアゴナル」 are rarely needed.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 斜めななめslanting
• 対角たいかくdiagonal
• 斜はすdiagonal
• 筋交いすじかいdiagonal
• ダイアゴナルdiagonal
• 対角線たいかくせんdiagonal (line)
• はすかいaslant