French term (edited): superposition (different situation)

this is where you can intrroduce another graphic on top of another one. or

I think it is perfectly normal to speak of different sets of data being 'superimposed' on the same (axes / ) graph; it may be used in a slightly figurative way, not specifically referrring to the exact graphic effect employed.

French term (edited): superposition (different situation)

And the relevant term might depend on context (CAD, GIS, graphics/photos, etc.), but I'd probably opt for "layering" if only to avoid the cognate.

LAYER: A usable subdivision of a dataset, generally containing objects of certain classes, for example rivers, roads or geology.
OVERLAY: The process of SUPERIMPOSING two or more maps, through registration to a common co-ordinate system, such that the resultant maps contain the data from both maps for selected features. Although the term overlay can be applied to paper based maps, more often it applies to the use of digital data, nevertheless, the principal is the same.
http://www.umass.edu/tei/ogia/parcelguide/Glossary.html

Chapter 4: LAYERS and SUPERIMPOSITION. Chapter 5: Superimposing Special Effects. ..... AutoCAD 2002: Tutor for Engineering Graphics, 1st Ed. ...
opamp.com/cf/keyword.cfm?SRow=1&Keywords=graphics

An extensive set of single map and multiple map LAYER transformations that produce spatial ... area based statistics, filtering, and LAYER SUPERIMPOSITION. ...
www.geo.tcu.edu/faculty/geosoftware2.html

Graphic SUPERIMPOSITION. The integration of two or more graphic sets in a .... Layer(s). A logical separation of mapped information according to theme. ...
www.gov.ns.ca/snsmr/land/standards/post/manual/appedxa3.asp

Layer: A subdivision of a CAD or GIS database containing related data. Layers can be visualized as transparencies which allow the user to view and analyze information selectively by theme. Some GIS build their databases as a SERIES OF LAYERS covering a single area. Layers are fundamental to OVERLAY analysis
[ ... ]
Data Merging - SUPERIMPOSING vector data on top of image data
www.kam.to/kam/services/gisdictionary.cfm

The LAYERING system should be based on the AIA CAD LAYER GUIDELINES, ...
www.victoria.ac.nz/fm/services/cad-standards/

LAYERING A method of logically organizing a computer graphics database by ‘overlaying’ each group of information one on top of the other.[ GLOSSARY OF GIS TERMS]
http://www.franklincountyohio.gov/auditor/Real_Estate/gis/Gl...

LAYERING - The process of placing one image on top of another and eliminating the lines underneath [Glossary of Digital Imaging Terms]
http://www.bayphoto.com/glossary/digglos.html

LAYERING (v) A scheme by which the various graphic elements of a drawing can be grouped together in the CAD database. This facility _is used most often to control what is seen _or editable on the screen and what is printed or plotted. Layering in most systems is nonhierarchical.
http://highered.mcgraw-hill.com/sites/0072322098/student_vie...


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Note added at 6 hrs (2008-01-08 01:13:34 GMT)
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To be sure of using the right term, you probably need to know what the graph is like.

For instance, it might be one showing man-hours per month for different customers. Now, you could have the time for company A, and over it, the time for company B. This would show you at a glance for which of the two companies you were working more in a given month. Or the computer might total the two times so you see at a glance the time you expect to be devoting to those two (this would not strictly speaking be "superposition", but I wouldn't put it past people to cross their wires). Two different approaches, possibly two different terms.

Or you might have man-hours per month devoted to milling frambuzzle nodulators, and man-hours devoted to polishing and deburring them, then the time taken to assemble them in pairs and screw in the brass knobs. With different graphic representations of all that and possibly different terms.