# What words to describe the three monomolecular structures

So there's technically 3 things a monomolecular structure can be:

• an edge a single atom thick which consists out of many molecules in a row to create the edge, often described for weapons with the sharpest edges.
• a structure made of a single molecule, like diamond or graphene
• (part of) an item that both has single atom thick edges and consists out of a single molecule.

Now I want to use all 3 possibilities in my stories but I don't want to just make up some name for each. I would want to have a somewhat scientifically correct nomenclature to describe each with one or two words. An example sentence:

"This sword is monomolecular so we know it has certain properties because of that".

Which word or words do I use to quickly describe each version of monomolecular? The shortest (preferably single word) answer for each with preferably an explanation why it is a good description for each type is the chosen answer.

• I've never heard "monomolecular" used to refer to the second case. More usually you'd call it a "crystal" or "polymer" or "alloy" or whatever describes its bulk composition and structure most succinctly. Jun 27 at 20:50
• Second bullet point can be either a polymer or a crystal, depending on what it actually is. (That is, if the substance is crystalline, then we speak of a crystal; if the substance is not crystalline we speak of a polymer. For example, a diamond is a crystal, but a piece of rubber is a polymer.) Note that most crystals are not really made up of molecules in any meaningful sense; most crystals cannot have a monomolecular edge, because they are not made up of molecules. Amorphous solids, such as glass, can. Jun 27 at 21:40
• I'm pretty sure that it'd been decided a few years ago that all "naming of things" questions are off-topic here as essentially opinion-based. Voting to close as such. From review. Jun 28 at 3:00
• @JiminyCricket. Which makes it a good thing that I am not asking for naming a thing, but how to differentiate between different ways to describe something. Just like there would be an answer to "how do I describe superheated air from normal air" there seem to be ways to describe my 3 states. So far Nosajimiki covers all 3 with the most correctness and just 1 or 2 words, which is in line with the question so unless a better answer comes along with more correct terminology it will be objectively the best answer, rather than opinion based. Links would complete the answer ofcourse. Jun 28 at 3:48
• What you're saying makes perfect sense, I'm too tired to do reviews with any certainty of geetting it right. Close vote withdrawn. Jun 28 at 4:00

an edge a single molecular thick which consists out of many molecules in a row to create the edge, often described for weapons with the sharpest edges.

Materials made out of many discrete molecules are called molecular solids. There are enough classifications for molecular solids though that you you generally wont differentiate what kind of molecular solid something is made of when talking about them; so, here you will simply prefix whatever you are talking about with the adjective monomolecular. IE: a monomolecular blade.

a structure made of a single molecule, like diamond or graphene

The scientific word for this is a covalent solid. Since the solid part is generally implied, you could use the adjective covalent. IE: a covalent blade.

That said, all covalent solids are crystals. Even though not all crystals are covalent solids, your audience is probably much more familiar with what a crystal is. When describing a covalent solid, you might choose to call it crystalline instead.

(part of) an item that both has single molecule thick edges and consists out of a single molecule.

Simply combine the terms it call it a monomolecular covalent blade or a monomolecular crystalline blade.

• "Not all crystals are technically pure covalent solids": Lots of crystals are held by ionic bonds, with no trace of covalent bonds. And, of course, calling metallic bonds "covalent" is a stretch. Jun 27 at 23:01
• @AlexP in fact, off the top of my head, diamond is the only crystal that is covalent. Wait, just remembered quartz! Still only two Jun 28 at 6:16
• Other materials with covalent solid crystal allotropes include germanium dioxide, silicon, silicon carbide, phosphorus, sulfur, and iodine... though not all of these have the same sort of utility or commonness as diamond or quartz; so, they tend to not get the same sort of attention. Jun 28 at 14:59

Monolayer - a 2D material 1 atom wide$$^1$$. I use this term a lot in my PhD work on 2D superconductors. It can be used as a noun ("this sword is a monolayer") or adjective ("a carbon monolayer sword"). Just figured I'd throw this jargon in there since it's actually my area of expertise.

As for your single-molecule covalent material, you could use "monomolecular" for that, though I personally think just using "covalent" is simpler and less ambiguous.

EDIT: If only the edge is monolayer-width, it might be better to go with something like monolayer-edged," or a shorthand like "monoblade" or "mono-edge." Thanks to Nosajimiki for pointing that out. I originally wrote a reply comment, but I figured it was important enough that it should be in the main answer.

$$^1$$ Well, technically one crystal cell wide, which could potentially be a few atoms thick, but the distinction doesn't seem to matter for your purposes.

• A monomolecular blade is not necessarily a monolayer. It simply means that the edge is honed to monomolecular precision. Jun 28 at 14:26

# Language Fails Me (Because This Isn't Important)

Consider the humble car tires. (In some places tyres...) Yes, the vulcanization process takes many smaller molecules and gets them to be one big, (possibly) happy molecule. Note that most people will say the tire is vulcanized instead of monomolecular!

The problem with big molecules is that size just doesn't matter so much in most scientific and engineering applications. Because it doesn't matter so much, we do not really have (in English) nice words to differentiate them. This is why it's "vulcanized rubber" instead of "monomolecular rubber." The process and ensuing properties from it are more important than molecular size.

Additionally, plastics are also described in terms of cross-linking type and degree of polymerization. This affects properties in a much more dramatic way than individual molecule size. This is also why we talk about vulcanization: it's a method to achieve a very high degree of cross linking.

In the world of crystals, you just refer to the thing as a "[crystal name] crystal". Maybe you talk about a specific form or lattice structure of crystals, but those usually have names. (Ex: "a quartz crystal" or "Smithsonite".)

This convention also goes the same for glass, but with the added benefit of talking more about composition than structure. (Because glasses lack repeating structure by their very definition!)

In the world of metals, we talk about localized areas of homogeny as "crystals" or "grains", even though these crystals/grains may have actual metallic bonds crossing over to form one big crystalline structure. Like glasses, metals are talked about more in terms of composition (or "grades") and temper. Sometimes the process is more important because you are talking about a category, so individuals prefer that. For example, steel can be rolled, forged, or cast and you would refer to those categories as such.

# TL:DR There Are No Words

There just isn't as much a demand for describing three different classes/uses of "monomolecular" with other words. We are more frequently more concerned with composition over size. You will need to have something made up to disambiguate these or just assume people will understand from context. (Because how often do you care if the tire has a sharp edge?)

You're going to have to give whatever words you choose a dictionary definition in your writing, because there isn't widely-accepted vocabulary that readers can get the meaning of based on their own experience. So you're wordsmithing to come up with a plausible, meaningful vocab. In which case, how about:

#1: an edge a single molecular thick which consists out of many molecules in a row to create the edge, often described for weapons with the sharpest edges.

Most of the suggestions start with mono-, but uni- or solus- would also make coherent prefixes, or something involving acies (Latin for "edge" or "line"). I quite like uniacic or acimolecular.

#2: a structure made of a single molecule, like diamond or graphene

Macromolecule might be a good word here, a molecule big enough to be seen on the macro scale.

#3: (part of) an item that both has single molecule thick edges and consists out of a single molecule.

This is probably best just given a compound definition. No reason why the uniacic edge of the macromolecule can't trip off the tongue...

The answer for the second ("made of a single molecule") is easier than the first, and none of the prior answers appears to have used it. The word you're looking for is probably monocrystalline. For example, monocrystalline silicon is a key raw material for the semiconductor industry precisely because it lacks the grain boundaries where electronic flow would be altered in polycrystalline materials.

As for the first ("edge as sharp as a single molecule"), various answers have proposed monomolecular. The problem you may run into is that, in various corners of hard sci-fi, "monomolecular" is typically an adjective used to describe a very fine wire which can then be used to cut things, being almost invisible (an advantage for its user) and causing dependably gruesome deaths (an advantage for the writer). I'd suggest a neologism here, such as "nanosharpened", if you're planning on lending this edge to knives and swords and such. But I'm probably over-thinking things and "monomolecular" might work just as well -- it's far more important that you show, not tell, just how damned sharp these things are.

• The turbine blades in high-performance jet engines are made from a single crystal/molecule each; the term used there is "single-crystal" Jun 28 at 15:13

These terms might be recognizable or at least decipherable by fans of the cyber-punk genre, if not SF in general. They may not work in scientific papers, but if your goal is to communicate these tropes within these fiction genres, to fans already literate in the genre’s tropes they should do. Trademark issues may still be a concern.

Mono-edged - an edge a single molecular thick which consists out of many molecules in a row to create the edge, often described for weapons with the sharpest edges.

Monocrystalline - a structure made of a single molecule, like diamond or graphene

Mono-honed - (part of) an item that both has single molecule thick edges and consists out of a single molecule

• As an aside, larger grain size in metal blades is not necessarily a good thing. A single large crystal would be very brittle. Rule of Cool though…
– unin
Jun 28 at 13:28

#1: an edge a single molecular thick which consists out of many molecules in a row to create the edge, often described for weapons with the sharpest edges.

Call this a monomolecular edge. Colloquially called a mono-edge

#2: a structure made of a single molecule, like diamond or graphene

A (structure made of a single) molecule is called a molecule.

#3: (part of) an item that both has single molecule thick edges and consists out of a single molecule.

This one makes no sense. Anything of type #2 is just a single molecule so is also a single molecule thick. Again it's just called a molecule. Also just a molecule.

Before knowing you were talking about a sword, considering the edge only, my mind immediately went to Polymer. Combining this with the answer of Stephen

Polyacimer, Monoacimer and Macroacimer