How to Format a Scientific Name in a Manuscript

How to format a scientific name in a manuscript

Capitalize the genus, keep the species epithet lowercase, and italicize both as a single unit — for example, Homo sapiens or Escherichia coli. After first use, abbreviate the genus to its first letter plus a period (E. coli). This applies whether the name is going into manuscript running text, an abstract, a figure legend, or a plain-text submission-system field.

Looking up the scientific name of a specific plant, animal, or microbe, rather than formatting one you already have? This guide will not help with that lookup — it is written for authors, editors, and manuscript preparers who already know the organism’s name and need to format it correctly for journal submission. For species identification, a taxonomic database such as the Integrated Taxonomic Information System (ITIS) or the Global Biodiversity Information Facility (GBIF) is the right destination.

1. Capitalize the genus.
2. Keep the species epithet lowercase.
3. Italicize both as a single unit.
4. Abbreviate the genus after first use (e.g., E. coli).
5. Do not abbreviate at the start of a sentence.

Subspecies, taxonomic authority citations, and higher taxonomic ranks like family or order follow separate rules, covered in the sections below.

This guide also covers the categories that trip authors up most before submission: bacterial and archaeal names under the ICNP, virus species names under the ICTV’s 2021 binomial rules, cultivar names in botany, and hybrid names — each governed by its own taxonomic code, with its own italics exceptions.

The core rule: genus capitalized, species lowercase, both italicized

A binomial (two-part) scientific name has a genus name and a specific epithet. In running manuscript text:

• The genus is capitalized: Homo, Escherichia, Quercus.
• The species epithet is always lowercase, even if it is derived from a proper noun (a person’s name or a place): sapiens, coli, alba.
• Both parts are italicized as a unit: Homo sapiens, Escherichia coli, Quercus alba.

This applies regardless of discipline — the same convention holds in medicine, microbiology, ecology, botany, and zoology manuscripts. It traces back to Linnaean binomial nomenclature and is now codified by the taxonomic governing bodies for each kingdom (see below), and in practice enforced through journal style guides such as the AMA Manual of Style (used widely in biomedical journals) and the Council of Science Editors (CSE) Scientific Style and Format manual.

Is Homo sapiens italicized? A worked example

Yes — Homo sapiens is always italicized, with the genus Homo capitalized and the species epithet sapiens lowercase. It follows the same binomial rule as any other species name; there is nothing special about it grammatically, but because it is the scientific name people encounter most often outside a biology context, it is also the one most often formatted wrong. Walking through it as a worked example:

• First mention in a manuscript: Homo sapiens (both words italicized, only the genus capitalized).
• Every mention after that: H. sapiens is acceptable (abbreviated genus, period, still italicized, species epithet still lowercase).
• Never: homo sapiens (genus must be capitalized), Homo Sapiens (species epithet must not be capitalized), or “Homo sapiens” set in plain roman type (both words must be italicized as a unit).
• The common name “humans” or “human beings” is not italicized or capitalized — only the formal binomial is.

The same worked logic — capitalize the genus, lowercase the species, italicize both, abbreviate the genus only after first use — applies identically to every binomial name in this guide, whether the organism is an animal, a plant, a bacterium, or (with the caveats below) a virus.

Abbreviating the genus after first use

Spell the genus name out in full the first time a species is mentioned in the text, the abstract, and typically also the title (check the specific journal’s instructions for authors on the title case). After that first full use, the genus may be abbreviated to its initial letter followed by a period, with the species epithet still lowercase and both still italicized:

• First mention: Escherichia coli
• Subsequent mentions: E. coli

Two situations where you should not abbreviate:

• At the start of a sentence. Most style guides discourage opening a sentence with an abbreviated genus; either spell it out again or restructure the sentence.
• When more than one genus in the paper starts with the same letter. If a manuscript discusses both Streptococcus and Staphylococcus, abbreviating both to S. creates ambiguity — spell out whichever is needed for clarity, or use a distinguishing abbreviation convention the journal permits.

What does and doesn’t get italicized

Only genus, species, and infraspecific epithets (subspecies, variety, forma) are italicized. Taxonomic ranks above genus — family, order, class, phylum — are set in regular (roman) type and capitalized as proper nouns, but not italicized:

• Italicized: Homo sapiens, Canis lupus familiaris
• Not italicized: Hominidae (family), Primates (order), Mammalia (class)

A related, frequently mishandled point: the abbreviations sp. (single unspecified species), spp. (multiple unspecified species), cf. (compare to, used when identification is uncertain), and sp. nov. / gen. nov. (newly described species/genus) are themselves set in regular roman type, not italics — even though they sit directly next to an italicized genus name. For example: Quercus sp. (an unidentified oak species) or Bacillus sp. nov. (a newly described Bacillus species). Common names derived from a scientific name — “E. coli infection” used loosely in prose, or vernacular names like “human” or “white oak” — are not italicized or capitalized as though they were the formal binomial.

Are bacteria names italicized? Species yes, strain designations no

Bacterial and archaeal names follow the same binomial rule as any other organism — genus capitalized, species lowercase, both italicized — and are governed for nomenclatural purposes by the International Code of Nomenclature of Prokaryotes (ICNP). So Escherichia coli, Staphylococcus aureus, and Mycobacterium tuberculosis are all italicized exactly like any plant or animal binomial.

What trips authors up is the strain designation that often follows the species name to identify the specific isolate used in an experiment — for example E. coli K-12, Staphylococcus aureus ATCC 25923, or Mycobacterium tuberculosis H37Rv. The strain code itself (K-12, an ATCC accession number, a lab-specific isolate ID) is set in roman, non-italic type; only the genus-species portion of the name is italicized. Writing the whole string — species name and strain code together — in italics is one of the most common formatting errors in microbiology manuscripts.

Are virus names italicized? Formal species names yes, common names no (ICTV, 2021+)

Virus nomenclature used to be far less consistent than the ICZN/ICN/ICNP world, but that changed in 2021, when the International Committee on Taxonomy of Viruses (ICTV) ratified a binomial format for formal virus species names — a genus name plus a “freeform” species epithet, both italicized, exactly like other binomials — with existing species names transitioned to the new format over the following several years. Real examples of the resulting formal species names: Lyssavirus rabies and Orthoflavivirus zikaense.

The catch for most authors: this binomial rule applies to the formal taxonomic species name, not to the familiar common (vernacular) virus name used in the overwhelming majority of clinical, applied, and public-health manuscripts. “Rabies virus” and “Zika virus” remain the everyday names for those same viruses, and common names are not italicized or capitalized as though they were the formal binomial — write “rabies virus caused…” in roman type, not “Rabies virus caused…”. Reserve the italicized formal species name (Lyssavirus rabies, Orthoflavivirus zikaense) for contexts that specifically discuss viral taxonomy or classification; a clinical or epidemiological paper about the disease itself will almost always use the common name instead.

Cultivar names: single quotes, not italics (ICNCP)

Cultivated plant varieties — a rose bred for a particular flower colour, an apple bred for a particular yield — are governed by the International Code of Nomenclature for Cultivated Plants (ICNCP), a separate code from the one governing wild-plant species names. A cultivar name (the “cultivar epithet”) is written in roman type, capitalized headline-style, and enclosed in single quotes, appended after the (italicized) genus and species, or after a non-italicized common name:

• Quercus alba ‘Fastigiata’ (species name italicized, cultivar epithet roman in single quotes)
• Rosa ‘Peace’ (genus alone, plus cultivar epithet)
• garden rose ‘Peace’ (common name, plus cultivar epithet)

The single quotes are not optional decoration — they are the formal marker that the following word is a cultivar epithet rather than a species or subspecies epithet, and the cultivar epithet itself is never italicized even when it directly follows an italicized species name.

Hybrid names and the multiplication sign (×)

A plant (or, less commonly, animal) hybrid is denoted with the multiplication sign × — not the letter “x” — which is itself set in roman type even when it sits between two italicized names. Two distinct forms show up in manuscripts:

• A hybrid formula, listing both parent species with × between them: Quercus alba × Quercus robur.
• A hybrid (nothospecies) binomial, where × sits immediately before the epithet inside the italicized name itself: Quercus × bebbiana. The epithet after × stays lowercase, exactly like any other species epithet.

Using a plain letter “x” instead of the multiplication sign is a common substitution error, especially when text is typed on a system without easy access to the × character or when a manuscript has passed through a find-and-replace pass that treated it as ordinary text.

Abbreviations used in scientific names: sp., spp., cf., aff., and nov.

A cluster of short Latin abbreviations shows up directly beside italicized genus and species names and is one of the most frequently mishandled details in manuscripts, because authors assume anything sitting next to an italicized name should also be italicized. It should not — all of the abbreviations below are set in roman type:

• sp. — a single, unidentified or unspecified species within a genus: Quercus sp.
• spp. — multiple, unspecified species within a genus: Quercus spp.
• cf. (confer, “compare to”) — used when a specimen closely resembles a named species but identification is not fully certain: Bacillus cf. subtilis.
• aff. (affinis, “affinity to”) — similar to cf., used when a specimen appears related to a named species without being confidently assigned to it: Streptomyces aff. griseus.
• nov. — a nomenclatural novelty marker for a name newly proposed in that publication, most often seen as sp. nov. (new species), gen. nov. (new genus), or comb. nov. (new combination): Bacillus subtilis sp. nov.

In every case, the genus (and species, where given) on either side of the abbreviation stays italicized as usual — only the Latin abbreviation itself is roman.

Subspecies and trinomial names

When a subspecies is specified, the name becomes a trinomial: genus, species, and subspecies epithet, all three italicized and all lowercase except the genus. For example, Canis lupus familiaris (the domestic dog, a subspecies of Canis lupus). In botany, an infraspecific rank abbreviation such as subsp. or var. is inserted between the species and infraspecific epithet and, like sp., is set in roman type rather than italics: Zea mays subsp. mexicana.

Taxonomic authority (author citation)

In taxonomic and systematics literature, a scientific name is often followed by the name of the person (or people) who first formally described the species and the year of publication, e.g. Homo sapiens Linnaeus, 1758. This author citation is set in regular roman type, not italics, and is not part of the italicized binomial itself. Most manuscripts outside taxonomy/systematics proper — clinical, ecological, or applied research papers that simply use an already-established species name — omit the author citation entirely; include it only if the species’ identity could otherwise be ambiguous or if the journal’s instructions for authors specifically request it.

Which code actually governs the name

For researchers describing a new taxon, formatting is governed by the applicable nomenclatural code, not by house style alone:

• The International Code of Zoological Nomenclature (ICZN) governs animal names.
• The International Code of Nomenclature for algae, fungi, and plants (ICN) governs those groups.
• The International Code of Nomenclature of Prokaryotes (ICNP) governs bacteria and archaea.

For the overwhelming majority of manuscripts — papers that use existing, already-published species names rather than formally describing a new one — a researcher does not need to consult these codes directly; following the journal’s house style (AMA, CSE, or the journal’s own instructions for authors) for capitalization, italics, and abbreviation is sufficient. The codes become directly relevant only when a manuscript formally proposes a new species or genus name, at which point the applicable code’s specific requirements for the description, type specimen, and name formation take priority.

Practical formatting in submission

• In Word: select the genus and species and apply italics (Ctrl+I) directly, rather than relying on autoformat or find-and-replace, which can silently miss instances.
• In LaTeX: use textit{} or emph{} around the binomial, not manual font-switching commands.
• Check plain-text fields separately. Submission systems (Editorial Manager, ScholarOne, and similar platforms) sometimes strip formatting from fields like the plain-text abstract or cover letter body, even when the manuscript file itself is correctly formatted — verify italics survived in every field the journal requires, not just the main manuscript document. The same italics can also be lost in figure legends and axis labels; see CASRAI’s guide to scientific figure rules for journal submission.
• Check the journal’s specific instructions for authors. Most biomedical and life-science journals default to AMA or CSE conventions, but some (particularly in botany and zoology) specify additional requirements, such as always including the author citation on first mention. For the surrounding manuscript formatting rules (margins, fonts, spacing) most journals also specify, see CASRAI’s research paper format guide.

Common mistakes to check for before submission

• Species epithet capitalized (Escherichia Coli — incorrect; should be Escherichia coli).
• Name not italicized at all, or italicized inconsistently across the manuscript.
• Genus abbreviated before it has been spelled out in full at first mention.
• sp., spp., or cf. italicized along with the genus name (they should not be).
• Family/order/class names (e.g., “Hominidae”) italicized as though they were genus-species names (they should not be).
• Author citation (e.g., “Linnaeus, 1758”) set in italics rather than roman type.

Right vs. wrong: 20 scientific names you can copy into a manuscript

A quick-reference table covering every category above — copy the “Correct” column directly.

Correct	Incorrect	Why
Homo sapiens	Homo Sapiens / homo sapiens	Genus capitalized, species lowercase, both italicized as a unit.
Homo sapiens (first use) → H. sapiens (later)	H. Sapiens	Abbreviated genus keeps the italics and the period; species epithet stays lowercase.
Escherichia coli	Escherichia Coli	Species epithet is always lowercase, even for a familiar organism.
E. coli K-12	E. coli K-12	Strain designations (K-12, ATCC numbers, isolate IDs) are roman, not italic.
Mycobacterium tuberculosis	mycobacterium Tuberculosis	Genus capitalized + italicized; species lowercase + italicized.
Lyssavirus rabies (formal ICTV species name)	Lyssavirus Rabies	Under the ICTV’s 2021 binomial rules, the virus species epithet is lowercase, like any other binomial.
rabies virus (common name, running text)	Rabies virus	The everyday common virus name is roman and lowercase — only the formal species binomial is italicized.
Orthoflavivirus zikaense (species) / Zika virus (common name)	Orthoflavivirus Zikaense	Same lowercase-epithet rule applies to newly assigned virus binomials.
Quercus alba ‘Fastigiata’	Quercus alba ‘Fastigiata’	Cultivar epithets are roman type in single quotes, even next to an italicized species name.
Rosa ‘Peace’	Rosa Peace	A cultivar epithet needs single quotes and roman type — it is not a species epithet.
Quercus alba × Quercus robur	Quercus alba x Quercus robur	Use the multiplication sign ×, not the letter “x”; the sign itself stays roman.
Quercus × bebbiana	Quercus x Bebbiana	× precedes the epithet inside a hybrid binomial; the epithet stays lowercase.
Canis lupus familiaris	Canis Lupus Familiaris	Only the genus is capitalized in a trinomial; species and subspecies epithets are lowercase.
Zea mays subsp. mexicana	Zea mays subsp. mexicana	The infraspecific rank abbreviation (subsp., var., f.) is roman, not italic.
Hominidae (family, roman type)	Hominidae	Family/order/class names are capitalized but not italicized.
Quercus sp.	Quercus sp.	“sp.” (one unidentified species) is roman, even beside an italicized genus.
Bacillus cf. subtilis	Bacillus cf. subtilis	“cf.” (identification uncertain) stays roman between two italicized names.
Streptomyces aff. griseus	Streptomyces aff. griseus	“aff.” (affinity to, not confirmed) is also roman type.
Bacillus subtilis sp. nov.	Bacillus subtilis sp. nov.	“nov.” markers for newly described taxa (sp. nov., gen. nov., comb. nov.) are roman.
Homo sapiens Linnaeus, 1758	Homo sapiens Linnaeus, 1758	The taxonomic author citation (name + year) is roman, not part of the italicized binomial.

Frequently asked questions

How do you write a scientific name in a manuscript?

Capitalize the genus, keep the species epithet lowercase, and italicize both as a unit — for example, Homo sapiens. Spell the genus out in full on first mention, then abbreviate to its initial letter (H. sapiens) afterward, unless doing so would create ambiguity with another genus discussed in the same paper.

Are scientific names italicized in APA and AMA style?

Yes. Both APA and AMA conventions italicize genus and species names. AMA’s rules (the more detailed of the two on this specific point, and the dominant style in biomedical journals) are covered above; for the broader mechanics of an APA-formatted manuscript, see CASRAI’s guide to writing a research paper in APA style.

Is the species name ever capitalized?

No. The species epithet is always lowercase in a properly formatted binomial name, even when it derives from a person’s name (e.g., victoriae) or a place name — only the genus is capitalized.

Do you italicize family, order, or class names?

No. Only genus, species, and infraspecific (subspecies/variety) epithets are italicized. Names for family, order, class, and higher taxonomic ranks are capitalized but set in regular roman type.

What is a trinomial scientific name?

A trinomial adds a subspecies epithet to the standard binomial — genus, species, and subspecies, all three italicized, with only the genus capitalized. Canis lupus familiaris is a common example.

Should Homo sapiens be italicized?

Yes. Homo sapiens is a standard binomial: the genus Homo is capitalized, the species epithet sapiens is lowercase, and both are italicized as a unit. After first mention it may be abbreviated to H. sapiens, still italicized.

Are bacteria names italicized?

Yes, the genus and species — Escherichia coli, Staphylococcus aureus — are italicized under the same binomial rule as any other organism, governed nomenclaturally by the ICNP. Strain designations that follow the species name (e.g., K-12, ATCC 25923) are set in roman type, not italics.

Are virus names italicized?

The formal two-word taxonomic species name assigned under the ICTV’s 2021 binomial rules is italicized (e.g., Lyssavirus rabies). The common, everyday virus name most manuscripts actually use — “rabies virus,” “Zika virus” — is not italicized.