1. Using Latin binomials and common names of organisms

Biologists often need to use both the Latin and the common names of organisms. Here is a simple guide to good practice.

1. At the first mention of an organism (e.g. baker's yeast), give its full Latin name (binomial) in italics or underlined: Saccharomyces cerevisiae or Saccharomyces cerevisiae. After that, you can write S. cerevisiae, or just Saccharomyces if it is clear to the reader that you are talking about only the one species of Saccharomyces.

2. If you use the common name of an organism, then you write dog whelk or rosebay willowherb, not Dog Whelk or Rosebay Willowherb. These are common names, as opposed to proper names, so they do not need Capital letters.

3. When you are talking about a Family, Order or Class (or any other hierarchical grouping of organisms above the level of genus) you use a Capital but do not use italics. For example, the frogs and toads are in the Class Amphibia, or just in the Amphibia. But when you write about these organisms in an essay, you can use the word 'amphibians' (a common name, without a Capital).

Here is a short section with several examples of correct usage. [I use square brackets for explanations]

"The amphibians [common name] are found mainly in moist habitats, whereas members of the Reptilia [proper name] occur in drier environments. Both groups are members of the Chordata [proper name] which encompasses [note that Chordata is singular] a wide range of animals, including humans. Chordates [common name, plural; note that it has a Capital only because it starts a sentence] are characterised by having an internal skeleton, in contrast to arthropods, which have an exoskeleton."

Here is one of the commonest errors.

Wrong: The Arachnida are found across the world.
Correct: Members of the Arachnida are found across the world.
Explanation: The Arachnida is a taxonomic group- one group - so you cannot talk about it as a plural.

4. A final point - you must always "respect" proper names. For example, the following are WRONG.

The Mucor sporangium is inflated. [Mucor is a proper noun, so it cannot be used as an adjective. Instead, write 'The sporangium of Mucor is inflated.']

Canis lupus's skull is large. [Write 'The skull of Canis lupus is large.]



There are only a few abbreviations that you will need to use.

  1. e.g. meaning 'for example' (for information, it comes from the Latin, exempli gratia)
  2. i.e. meaning 'that is' (from the Latin id est). Note that 'i.e.' specifies particular things, whereas 'e.g.' gives examples.
  3. etc. meaning 'and so forth' (from the Latin et cetera) [Some people, wrongly, write ect.]
  4. et al. meaning 'and others' (from the Latin et alia). You would use this only when citing references.

Normally, you would use i.e. and e.g. in brackets or within dashes, as in the following examples.

Several ions (e.g. chloride, nitrate) were found to interfere with the assay.
Several ions - e.g. chloride, nitrate - were found to interfere with the assay.
The larger of the two bacteria (i.e. Bacillus cereus) was found to grow faster.
The larger of the two bacteria - i.e. Bacillus cereus - was found to grow faster.

[Incidentally, you might notice that putting something in italics - as you might do for the heading or subheading of an essay - fails to distinguish a Latin word or name (Bacillus cereus) from the rest. The solution that many scientific journals adopt is to put the Latin word in normal typeface (termed Roman typeface). For example, a heading could be: The bacterium Bacillus cereus and other food-poisoning organisms.]

A few points about spelling

Word endings: -ise and -ize

Often the choice of -ise or -ise is optional. But, increasingly we are moving towards -ise as the preferred option. Thus: optimise, theorise, hypothesise, plagiarise, equalise, etc.

Hyphenated words

There are no simple rules governing the use of hyphens (un-coordinated, well-written, etc.), so judgment and common sense are required. Many scientific journals, especially in the USA, discourage the use of even well-chosen hyphenated words. But imagine that last sentence without the hyphen; you would have a string of descriptive words (even, well, chosen, hyphenated) to sort out for yourself.

In general, hyphens should be used only to avoid confusion of meaning. For example:

  • a walking-stick certainly is different from a walking stick, but a reader is unlikely to be confused if you miss out the hyphen;
  • it is normal to write ninety-first (and similar) instead of ninety first;
  • it makes sense to use hyphens for compound adjectives (e.g. a gorse-covered hill, a well-chosen site, a time-limited offer);
  • the Edinburgh-Glasgow railway line is different from the Edinburgh Glasgow line;
  • a black-backed jackal is different from a black backed jackal (which must be black all over, as well as having a back)
  • it is usual to hyphenate when a noun is used as an adjective (e.g. tooth-decay, mountain-bike);
  • the prefix 'non-' is often hyphenated (e.g. non-usable, non-stick, non-smoker) but 'un-' is usually non-hyphenated (unusable, unstuck, unexciting);
  • times such as 9 o' clock (9 of the clock) should not be hyphenated;
  • you might be alarmed if you read in your coursebook the instruction "Tonight you should look up the rectum" - even if that is technically correct, it would be sensible to hyphenate (look-up) the compound verb (to look up, meaning to consult)!

Advice: Instead of using hyphens, think about joining the words together if this seems reasonable. For example, a web site (or web-site) could equally well be a website. If you type 'website' in a Windows program (which, incidentally, is the proper spelling of programme when you are referring to computers) then the Spelling Tool will tell you it is wrong. But it will be the norm in 5 years time. Wake up, Bill Gates!

Some anglicised Latin words: singular and plural

Many people have problems with the singular and plural forms of Latin and Greek words - and understandably so!

In most cases you just have to learn the terms. But there are a few rules to (partly) help you.

  1. There are five common endings to the singular form: -a (as in alga), -us (as in fungus), -um (as in bacterium), -is (as in hypothesis), -on (Greek, as in mitochondrion).
  2. Each of these has its own plural form: -ae (as in algae), -i (as in fungi), -a (as in bacteria), -es (as in hypotheses), -a (Greek, as in mitochondria).


  • One alga, several algae. (and similarly for corona, papilla).
  • One fungus, several fungi (and similarly for pilus, locus).
  • One bacterium, several bacteria (and similarly for sporangium, cerebellum, medium, datum - yes, data is the plural form).
  • One hypothesis, several hypotheses (and similarly for thesis, prognosis, diagnosis, proboscis, testis).
  • One mitochondrion, several mitochondria (similarly for phenomenon, protozoon)

The following table lists some of the commoner terms.

Singular Plural Comments
alga algae  
ascus asci  
bacterium bacteria  
chaeta chaetae  
datum (seldom used) data Write "these data", "the data show"
fimbria fimbriae  
flagellum flagella  
fungus fungi  
genus genera  
hypha hyphae  
labium labia  
locus loci  
maxilla maxillae  
medium media Never write "this culture media"
mitochondrion mitochondria  
septum septa A septum, several septa
phenomenon phenomena We noticed a phenomenon.
phylum phyla  
pilus pili  
podium podia  
protozoan (or protozoon) protozoa  
pseudopodium pseudopodia  
seta setae  
sporangium sporangia  
stoma stomata Leaves have stomata (but, stomates according to Americans)
taxon (any taxonomic category) taxa  
none   None means "not one". So you write "none is", not "none are".

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Spelling - some commonly misspelt words

Correct Wrong (or, at least, not what you meant!)
accommodation, accommodate accomodation
acknowledge aknowledge
acquire aquire
address, addressed adress
affect (verb - to influence something) (see also effect further down this list) effect (as a verb) - when you affect (verb) something you cause an effect (noun)
attach, attached attatch, attatched
beginning begining
changeable changable
carnivorous (and herbivorous, omnivorous) carniverous, herbiverous, omniverous
conceive concieve
current (present, now) currant (a thing you find in a bun)
deleterious deliterious
dependent (this is a participle - something is dependent on something else; e.g. children are dependent on their parents) dependant (but correct as a noun - a person who depends on another; e.g. children are dependants)
desert (a dry place) dessert (not a dry place) something you eat in a pretentious restaurant
desperate desparate
desiccate, desiccation dessicate, dessication
deterrent deterent
develop develope
disappear dissappear
effect (usually a noun, but used as a verb in a very restricted sense- e.g. to effect (bring about) a change)  
environment enviroment
existence existance
favour favor (American spelling)
gauge (e.g. to judge something, or a thing that measures) guage
independent independant
inoculate innoculate
led (verb - the form used in the past tense; e.g. it led to or he led me) lead (the present tense of the verb; e.g. I lead a good life) but often wrongly used in place of led
licence (noun, e.g. driving licence) license (this is correct as a verb - to permit or authorise)
lie (verb - let sleeping dogs lie, to lie on a bed). It becomes laid or lay in the past tense (yesterday the dogs lay for hours; I laid it down) lay (what hens do), becomes layed in the past tense
lose (to lose something) loose (your clothing can be loose)
maintenance maintainance
may be (e.g. It may be blue, or correct, etc.) maybe (this means perhaps; it does not mean may be)
occur, occurred, occurrence occured, occurence
omnivorous omniverous
possess (own) posses, posess
practice (noun - a doctor's practice) practise
practise (verb - a doctor practises, and so does a juggler if he wants to be good)  
privilege privalege, privaledge
principal (main)  
principle (one of those rules you hold dear)  
proceed procede
receive recieve
separate (remember that you can separate a pair) seperate
stationary (still) stationery (paper, sold by a stationer)
supersede (to replace) supercede, superceed
succeed, success  
taxonomic (because a group is a taxon) taxanomic
tumour tumor (American spelling)
unmistakable unmistakeable