“Scientific nomenclature” is not one system — it is a family of separate, independently governed naming conventions, and a manuscript that mixes disciplines may need to follow more than one of them correctly at once. A microbiology paper naming both an organism (Escherichia coli) and a gene it expresses (lacZ) is using two different nomenclature systems in the same sentence, each with its own formatting rule and its own governing body. This guide works through examples from the three systems a researcher is most likely to encounter — biological (binomial) nomenclature, chemical nomenclature, and gene/protein nomenclature — so the differences, not just each system in isolation, are clear.
Biological (binomial) nomenclature: species names
The most familiar system, governed by Linnaean binomial convention and codified today by discipline-specific codes (the International Code of Zoological Nomenclature for animals, the International Code of Nomenclature for algae, fungi, and plants, and the International Code of Nomenclature of Prokaryotes for bacteria and archaea). The rule: genus capitalized, species epithet lowercase, both italicized as a unit.
- Homo sapiens — genus Homo, species sapiens.
- Escherichia coli, abbreviated E. coli after first mention.
- Canis lupus familiaris — a trinomial, adding a subspecies epithet.
This is deep, mechanical territory with its own rules for abbreviation, subspecies, and taxonomic authority citations — covered in full in CASRAI’s guide to how to write a scientific name. The rest of this page focuses on the two nomenclature systems that guide does not cover.
Chemical nomenclature: IUPAC names
Chemical compounds are named under rules set by the International Union of Pure and Applied Chemistry (IUPAC). Unlike a binomial species name, an IUPAC name is not a fixed pair of words — it is systematically constructed from the compound’s actual molecular structure, so the name itself encodes the chemistry. The same substance often also has one or more common (trivial) names that are shorter and more familiar but structurally uninformative.
- Ethanoic acid (IUPAC systematic name) is the common laboratory chemical usually called acetic acid (trivial name) — the main component of vinegar.
- 2-acetoxybenzoic acid is the systematic name for acetylsalicylic acid, marketed and commonly written as aspirin.
- Propan-2-one is the systematic name for the solvent more commonly called acetone.
Formatting conventions specific to chemical nomenclature that differ sharply from binomial names:
- No italics by default. A systematic chemical name is set in regular roman type. Italics are reserved for specific structural descriptors within a name — stereochemical locants such as cis-, trans-, R-, S-, and ring-fusion or replacement prefixes like N– or O– (as in N-methylacetamide) — not the compound name as a whole.
- Locants and multiplying prefixes are structural, not decorative. Numbers, hyphens, and prefixes such as di-, tri-, and tetra- specify exactly where a substituent sits on the parent chain or ring; dropping or misplacing one changes what compound the name describes, which has no equivalent risk in a species name.
- CAS Registry Numbers supplement, rather than replace, the systematic name. Many journals in chemistry, pharmacology, and toxicology ask authors to give a compound’s CAS Registry Number (a unique numeric identifier assigned by Chemical Abstracts Service) alongside its name on first mention, precisely because trivial names and even systematic names can be ambiguous across sources in ways a registry number is not.
For manuscripts naming a genuinely novel compound, IUPAC’s own nomenclature recommendations (published as the “Blue Book” for organic chemistry and the “Red Book” for inorganic chemistry) govern construction of the name; for a manuscript simply using an already-established compound name, following the journal’s house style and confirming systematic-name/trivial-name consistency is normally sufficient.
Gene and protein nomenclature
Genetics and molecular biology manuscripts follow a nomenclature system with its own governing bodies and its own formatting distinction — one that trips up authors specifically because it looks similar to binomial species formatting without being the same rule.
- Human gene symbols are italicized; the proteins those genes encode are not. The gene TP53 (italicized, all capitals) encodes the protein p53 (roman type, lowercase p). Writing “the TP53 protein” in roman type when referring to the gene, or italicizing “p53” when referring to the protein, is a common and journal-flagged error.
- Species-specific capitalization conventions differ. Human gene symbols are conventionally written in all capitals (TP53), while mouse gene symbols follow a different house convention — only the first letter capitalized (Tp53) — under Mouse Genome Informatics (MGI) guidelines. A manuscript comparing a gene across species needs to apply the correct species-specific convention for each one, not one convention throughout.
- Human gene names and symbols are assigned by the HUGO Gene Nomenclature Committee (HGNC), the body responsible for approving a unique, standardized symbol for every known human gene — the reason a gene symbol such as BRCA1 refers unambiguously to one specific locus across the literature rather than varying by lab or paper.
As with chemical nomenclature, the underlying rule is not arbitrary house style — HGNC’s approved symbol and MGI’s species-specific conventions are the actual governing standards a manuscript is expected to follow, with journal style guides (AMA, CSE) layering formatting requirements such as italicization on top.
Comparing the three systems at a glance
| System | Governing body | Formatting signal | Example |
|---|---|---|---|
| Binomial species names | ICZN / ICN / ICNP | Genus + species, both italicized; genus capitalized | Escherichia coli |
| Chemical compounds | IUPAC | Roman type; structural locants/prefixes are load-bearing, not italicized (except specific stereodescriptors) | Ethanoic acid (= acetic acid) |
| Human genes vs. proteins | HGNC (genes); species-specific conventions for proteins | Gene symbol italicized and capitalized; protein product roman type | TP53 gene → p53 protein |
Why the distinction matters in a manuscript
Each of these systems exists to solve the same underlying problem — letting researchers refer to the same entity unambiguously across a literature spanning decades and thousands of journals — but they solve it through different mechanisms, so the formatting that signals correctness in one system can be meaningless or actively wrong in another. Italicizing a chemical compound name the way a species name is italicized, or failing to distinguish a gene symbol from its protein product, are both errors a copy editor or reviewer is likely to flag, independent of whether the underlying science is sound. Getting the convention right is also an indexing and searchability issue: databases such as PubMed, ChemIDplus, and gene databases like NCBI Gene rely on consistent nomenclature to link a manuscript to the correct entity record.
Frequently asked questions
What are examples of scientific nomenclature?
Homo sapiens (binomial species name), ethanoic acid / acetic acid (IUPAC chemical nomenclature), and TP53 as a gene symbol versus p53 as its protein product (gene/protein nomenclature) are examples from three separate, independently governed naming systems, each with its own formatting rule.
What are the different types of scientific nomenclature?
The three a researcher is most likely to need in a manuscript are biological (binomial) nomenclature for species, chemical nomenclature (IUPAC) for compounds, and gene/protein nomenclature for genetic elements and their products. Other specialized systems exist — astronomical object designations, mineral nomenclature — but are relevant mainly within their own disciplines.
Is chemical nomenclature italicized like a species name?
No. A systematic chemical (IUPAC) name is set in regular roman type. Italics in a chemical name are reserved for specific stereochemical locants and structural prefixes (cis-, trans-, N-, R-, S-), not the compound name as a whole — unlike a binomial species name, which is italicized in its entirety.
How is a gene name different from a protein name in formatting?
The gene symbol is italicized (e.g., TP53); the protein product it encodes is set in roman type (p53). This distinction is specific to gene/protein nomenclature and does not carry over from binomial species formatting, even though both use italics as a signal.
Who governs gene naming conventions?
For human genes, the HUGO Gene Nomenclature Committee (HGNC) approves a unique standardized symbol and name for each gene. Other species follow their own conventions — for example, Mouse Genome Informatics (MGI) for mouse genes — which is why the same gene can be styled differently (TP53 in humans, Tp53 in mice) depending on the organism being described.
