The best replacement for diagrams is flowcharts.

The best alternatives to diagrams are rated as following:
★★★★★  flowcharts
★★★★  charts
★★  fishbone diagrams
★★  sequence diagrams
★★  schematics
★★  entity relationship diagrams
★★  erd
★  data flow diagrams
★  er diagrams
★  collaboration diagrams
★  physical network diagrams
  communication diagrams
  organization charts
  use cases
  ladder diagrams
  flow charts

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Speaking about diagrams, one probably shouldn't forget about instructions.

Other search terms related to diagrams and their ratings are:
★★★★★ instructions
★ probability
You have in mind a companion for diagrams and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of diagrams in all years. Click on graph for more.
diagrams
flowcharts
charts