I'm searching for a noun (a single word if possible) or phrase that conveys that one thing functions the same as another externally, even though the internals may differ.

Nouns such as copy, a clone, duplicate, or substitute capture only part of my meaning. Additionally, these words often have a negative connotation; they imply that the thing is derived and possibly inferior. But I don't want to imply that the other thing is derived or merely copied.

What might be some good words or phrases that give a positive connotation, perhaps giving a sense of rethinking, "re-invention", or possibly renewal? I don't need the word to necessarily signify that the new thing is alive, but I want to avoid implying that it is 'lesser'.

Here is an example sentence:

LEG, a recent upstart in the electronics industry, has released the Tintium line of microprocessors, a [?] of Intel's Pentium line of processors. It behaves identically, but since it uses tin-arsenide for its substrate, the chips offer better reliability, especially for interstellar applications. The chip design is open source; several industry experts claim its internals are simpler and more efficient than the Pentium.

And another:

After losing his biological leg, Alan sought the services of Biocraft LLC, who custom designed and attached a [?] of his original limb. The company says it will outlast the natural leg.

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    Something like an enhancement. – jxh Jan 22 '15 at 23:01

12 Answers 12


The word analogue lacks a negative connotation and appears to convey your intended meaning well.

In your example sentences:

"...released the Tintium line of microprocessors, an analogue of Intel's Pentium line."

"...sought the services of Biocraft LLC, who custom designed and attached a prosthetic analogue of his original limb."

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    An analogue digital device is oxymoronic. – dangph Jan 23 '15 at 7:09
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    Because of the word's other technology-related meaning? When used in that sense, the American spelling of analog is preferred. I do see your point though. It could be a source of confusion if a reader is unfamiliar with the multiple meanings of the word. – pyobum Jan 23 '15 at 7:29

The word you're looking for is emulate.

verb. 1. match or surpass (a person or achievement), typically by imitation.
"most rulers wished to emulate Alexander the Great"
"hers is not a hairstyle I wish to emulate"
2. reproduce the function or action of (a different computer, software system, etc.).
"the adaptor is factory set to emulate a Hercules graphics board"

Adapted from Google's definition

If what you want it as a noun, then I'd go with: emulation or even, emulator

It certainly connotes a desire to be similar in a positive sense, out of awe or respect.

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    The noun "emulation" is usually used to describe the actions of someone - not an object. (I did that Ngram thingy to check) – Oldbag Jan 23 '15 at 13:54
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    @Oldbag try emulator – Pureferret Jan 23 '15 at 13:55
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    In software, the result of an emulation is often slower or otherwise inferior to the original, so this is not free from negative connotations. (In software, I would consider a clone to possibly work better than an emulation.) – skymningen Jan 23 '15 at 13:59
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    @Pureferret - Yeah, that's better... But, it still gives me the sense that the latter is "trying to keep up" with the original, whereas, "analogue" (which I up-voted) or "alternative" (which I suggested) implies "another of the same kind of thing". – Oldbag Jan 23 '15 at 14:02
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    @skymninge I don't see that here, in my experience emulators often run on better hardware giving an overal increase in performance – Pureferret Jan 23 '15 at 14:04

Consider a drop-in replacement.


I find it difficult to suggest a word that fits both contexts exactly the same. You may have to tailor it to your specific context.

For the leg, replica comes to mind: as a faithful reproduction it may look the same, but the construction can be different.

For the microprocessor, maybe "an improvement on Intel's Pentium line..." This suggests it had a similar ancestry, but changes course and surpasses the older model.

If this were a person you were talking about, I'd suggest a double or doppelgänger. This connotes extreme outward similarity, but doesn't lessen its importance, and even calls into question the difference in motives.

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    Replica for the leg example, +1. – Mazura Jul 17 '15 at 22:49

Perhaps simulation

Representation of the operation or features of one process or system through the use of another: computer simulation of an in-flight emergency.

American Heritage

The term is widely used in technology for things that mimic the function of a more naturalistic object or event. The term seems to be neutral, but may take on positive or negative tones with adjectives.

For example, Beatlemania was a tribute musical featuring Beatle look-alikes and songs. It billed itself as Not The Beatles, But an Incredible Simulation.

A related term is simulator

One that simulates, especially an apparatus that generates test conditions approximating actual or operational conditions.

American Heritage

This seems to be more often applied to a test device that is not intended to take the place of an actual device or situation.

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    Interesting, but simulations aren't direct substitutes for the real thing, are they? (Notwithstanding The Matrix.) – David J. Jan 22 '15 at 21:19

"... the/an equal of/to Pentium's ..." might work as a noun for your first example, or "..., which equals Pentium's ..." as a verb. This would avoid the negative connotation, but it might limit your freedom to discuss how much better it is.

Your second example would, in my opinion, require qualification: "... an/the equal in many respects of/to ..." The "which equals in many respects" verb form would require mentioning first the artificial limb.
IMO, it's going to be hard to describe an artificial limb without some hint of negativity vis-a-vis the real thing, however.


Instead of "a __ of...", if you use "an __ to..." you could fill in the blank with alternative.

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    an alternative may be something quite different. – AverageGatsby Jan 23 '15 at 14:16
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    "An "alternative" would be something "different" by definition. The implication is that it serves the same purpose. – Oldbag Jan 23 '15 at 14:33
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    With "quite" i mean completely. "An alternative to guessing is checking dictionaries". Does it serve the same purpose? In some way. Another example from TFD: "A choice or course of action that is mutually exclusive with another: The alternative to staying in that dead-end job is to quit." – AverageGatsby Jan 23 '15 at 15:16
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    I see what you're saying... Although I believe context would eliminate the possible ambiguity. – Oldbag Jan 23 '15 at 15:22
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    "An alternative to his original limb" sounds a bit weird. Maybe he is getting a rifle attached to his shoulder. Sorry. – AverageGatsby Jan 23 '15 at 15:25

Something that "functions the same as another externally, even though the internals may differ" can be called a look-alike or act-alike. The artificial leg could be called a simulacrum or replica of the original, though perhaps none match exactly. There is the noun reinvention.


Here is how I would consider handling these sentences:

LEG, a recent upstart in the electronics industry, has released the Tintium line of microprocessors, {the equivalent of / a substitute for / which emulates / which is analogous to} Intel's Pentium line of processors.

You wrote that in your view, 'substitute' implies a copy, or an inferior or derivative version, and is an unsuitable word choice for that reason.

But as the Tintium "behaves identically" to the Pentium line of processors, to that extent the connotation "something copied" does seem applicable here, and 'substitute' is therefore a valid possibility.

After losing his biological leg, Alan sought the services of Biocraft LLC, who custom designed and attached a replacement for his original limb.


I'd suggest twin as the noun you're looking for - it works in both of your examples, it has no negative connotation I'm aware of, and it literally means a copy (not merely "something similar to").

I think, however, that your first example wants to imply something a bit more involved than mere similarity, as the subsequent sentences go on to describe how the LEG chip is different from the Intel one. A writer of such a paragraph would probably use a noun like "competitor" or "challenger" to emphasize that the new chip is in the same market/class as the Pentium but has different features.


When something is functionally identical to another thing, as with your processor example, we simply say it's functionally identical. If there are exceptions, as there are with the processor example, then you would state them, as you have.

If it has superficial resemblance to another thing, as with your leg example, we might say the replacement is a simulacrum of the original

a slight, unreal, or superficial likeness or semblance. (Dictionary.com)

We might also refer to the replacement as a facsimile of the original, but, strictly speaking, that means exact copy. You might use that if there is no noticeable difference. This wouldn't apply to the processor, because there is a noticeable difference in how it behaves after exposure to radiation of space travel.


Improved copy is a standard term for that.

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