# What's the difference between superpose and superimpose?

The definitions seem very much alike:

superposed - Place (something) on or above something else, esp. so that they coincide: "superposed triangles".

superimpose - Place or lay (one thing) over another, typically so that both are still evident.

Are they just synonyms?

• I am using the term superimposed perception (superimpositoception) to refer to the form of organism perception where neuro-electromagnetic radiation is absorbed during different flux phases from other organisms. The im- prefix was most appropriate in my use because it indicates something positioned inside an organism (as in stimulation/modulation cycle of an organism's sensory modes). Commented Sep 9, 2021 at 17:24

They are synonyms but have different scopes of usage.

Superimpose is the term found in general use.

Superpose is used mostly in scientific or mathematical contexts; see 'superposition'.

Merriam-Webster has them as synonyms, but the difference is this: consider the Star of David, and consider the construction of one with two solid triangles rather than interlocking triangles.

The two triangles are superimposed, and both are evident.

Were one triangle not rotated, they would be superposed.

• This is true in mathematics; in geology there is yet another usage, referring to the stratification of layers. Commented Mar 13, 2012 at 14:35
• I'm no mathematician, so maybe I'm wrong here, but this seems unlikely to me. In this diagram, the two (implied 3-d) triangles are interlaced, or interwoven. I'd be genuinely surprised if the mathematical usage distinguished between these two words according to visibility from the particular vantage point of the observer. Commented Mar 13, 2012 at 15:56
• @FumbleFingers, that is why I said consider the construction of one with two solid triangles rather than interlocking triangles. Commented Mar 13, 2012 at 16:06
• I still don't understand. Are you saying that to a mathematician (are you one?) there would be two different ways of arranging the triangles (whether 2-d, 3-d, or "Escherian") such that superimposed/superposed unambiguously distinguishes between the two? Commented Mar 13, 2012 at 16:21
• I am not a mathematician, nor do I play one on television. Yes I am saying that, and the Star of David was the first commonplace geometric structure that came to mind. I have seen Stars of David wherein it is not evident that the triangles interlock, so I wanted to make the distinction, especially after replacing my original (very large) image with an interlocking version. Commented Mar 13, 2012 at 17:41

I am an American mathematician who would have liked to comment on Cornbread Ninja's answer, but I have no experience points and so am giving an "answer" instead. The variability in usage of both terms is so great that extracting a true distinction seems useless. A reading of the OED definition of each has led to me sympathize a little with Cornbread Ninja's answer. But the 'interlacing' of the triangles in Cornbread Ninja's example seems to obfuscate the distinction being described. The distinction is that superimposed triangles have not merged. Superposed triangles would meld together. In physics and mathematics we speak of the `superposition' of waves. For example, light is a superposition of electromagnetic waves at different frequencies. Different frequencies correspond to different colors. The colors meld together and cannot be distinguished (without a prism for example). So superposition makes sense in this context. In contrast, superimposition would be exemplified by placing pieces of colored pieces of construction paper upon one another.

Superimposed = one image overlying another.

Superposed = the addition of one image to another, e.g. mean water level = 5mOD

Waves = +/- 1m above mean level

Superposed = water level between +4mOD and +6mOD

I think there are two distinct concepts, but they are confused by using both terms. In Geology the law of superposition states that in undeformed strata the oldest materials lie at the bottom and are OVERLAIN (but not combined - thus altering characteristics) by younger layers that are subsequently deposited over them

BUT

In discussing waves, the superposition of waves of different frequency (sound, light, or electrical) results in a new waveform that combines the charactersitrics of both waves.

I'm inclined to use superimposition for the former (despite the well-know geologic law of superposition - not superimposition) and superposition for the latter.

So if one superimposed a red triangle on a blue circle - both made of construction paper - the only parts of the blue circle that would be visible are those not "covered" by the triangle (ie. those parts over which the triangle was not superimposed). I think of superimposing, say, images, as suggesting the image that is superimposed on another is opaque (like subtitles) covering the part of the image on which another has been supermposed - like superimposing (not superposing) the image of an actor in front of greenscreen on a background image.