also: ダイヤグラム
noun
A schematic drawing or plan that explains something, such as a chart, graph, or technical illustration.
このダイアグラムを見れば、システムの構造が一目でわかる。
Looking at this diagram, you can understand the system's structure at a glance.
Standard katakana spelling; the most common form.
Alternate katakana spelling; less common but still used.
図 is a broader native Japanese term for any figure, drawing, or illustration, while ダイアグラム specifically refers to a schematic or explanatory diagram.
グラフ is a graph or chart, often with axes and plotted data, whereas ダイアグラム is a more general diagram that may include flowcharts, network diagrams, etc.
Loanword from English 'diagram'.