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Commas are allowed in FSNs when required to provide meaning. They are not allowed when used to order words in a text string to enable a search function. 

For example:

  • Yes = when clarifying meaning in multiple parts: Head, neck and chest)
  • No = when being used to modify "sort" order | Frostbite, acute | Apostrophes

Eponymous terms should ideally not include an apostrophe or final "s" (unless the name normally ends in "s"). With rare exceptions, concepts with any eponymous terms should have at least one term that follows this rule.


  • Down syndrome
  • Sjogren syndrome
  • Meigs syndrome

On the other hand, in common usage the preferred name frequently does include the apostrophe "s". Where common usage requires it, there should be at least one term that has the apostrophe "s". Existing eponymous terms with the possessive "s" but no apostrophe need not be retired, but newly added terms should either have no "s", or else include the apostrophe. For terms with a possessive apostrophe where the name normally ends in "s", the apostrophe should of course follow the "s". There should be no hyphen in between the two words.


  • Alzheimer's disease
  • Bowen's disease
  • Reiter's disease
  • Meigs' syndrome Special characters

The special characters <, >, &, %, $, @, # are not permitted in FSNs. All instances of FSNs containing any of these characters need to be spelled out in full text. E.g. "FD&C Yellow #2" should be "FD and C Yellow Number Two".

The characters @ and $ are not used in any active term, regardless of term type, and new descriptions containing these characters should be avoided.

The characters &, %, and # are legitimately used in some synonyms including preferred terms. Hyphens and dashes

A hyphen is a punctuation mark used to join words and to separate syllables. There should be no spaces either before or after the hyphen. Hyphens should follow rules of style for the dialect and language in which the terms are used.


  • intra-articular
  • Zollinger-Ellison syndrome
  • Zellweger's-like syndrome
  • tick-borne hemorrhagic fever
  • phospho-2-dehydro-3-deoxygluconate aldolase

A dash is also a punctuation mark, but is used differently from a hyphen. It may be used to separate two phrases or names, to contrast values, to show a Relationship between two things, or to separate ranges of values.

Dashes (as opposed to hyphens) should not be used in FSNs (with rare exceptions) because they may obscure the exact meaning of the term. The dash should be replaced with words that clarify the meaning.

Table 85: Examples of dashes that should not be used in FSNs, and a replacement phrase:

Not acceptable for FSN:

Use instead:

Y90 - Yttrium 90

Yttrium 90

Aeronautical engineer - feasability studies

Aeronautical engineer involved in feasibility studies

On examination - breath urinose - uremic

on examination, breath urinose implying uremic subject

O/E - bowel sounds exaggerated 

On examination, bowel sounds exaggerated

Disability - all limbs Disability of all limbs

Exceptions to the use of dashes: Where there is a need to distinguish categories from more specific subtypes that have the same name, it is sometimes expedient to use a dash followed by the word "category". For example, "glioma - category" distinguishes the general category of all gliomas from those neoplasms that are called simply "glioma". The neoplasm specifically called "glioma" is one of several subtypes of the glioma category, and does not have the same meaning as the category itself. Many classifications distinguish the category from the subtype of the same name by using a plural for the category. For example, ChEBI has a category called "amphetamines" and a specific molecular entity called "amphetamine". Colons

Colons should not be used in FSNs.

Colons are allowed in the FSNs of organisms, substances, or products where the colon is a proper part of the name. They are also allowed in ratios and in tumor stages.


  • Salmonella II 43:g,t:[1,5] (organism)
  • lidocaine hydrochloride 1.5%/epinephrine 1:200,000 injection solution vial (product)
  • pT3: tumor invades adventitia (esophagus)

Colons are allowed in designations (non-FSN terms) in a variety of contexts. Some common examples of use are to separate acronyms from the rest of a name, and to separate a specimen from the finding identified in that specimen.


  • FH: Metabolic disorder
  • H/O: breast problem
  • Urine: red - blood Forward slashes

The forward slash should not be used in FSNs. In cases where the slash is part of the authoritative name (e.g. representation of heterozygosity in hemoglobinopathies), a hyphen (no space before or after) shall be used in the FSN; however, the forward slash, without spaces, may be used as part of the preferred term.

For example:

  • FSN: Hemoglobin D-beta thalassemia
  • PT: Hemoglobin D/beta thalassemia

Exceptions: A forward slash may be used for representing units of measure, as required in the pharmaceutical products hierarchy, and in laboratory test results and units of measure hierarchies. They may also be used in the construct "and/or" in FSNs. There should be no space either before or after the slash.


  • Nitroglycerin 0.3mg/hr disc (product)
  • Mesoridazine besylate 25mg/mL injection solution ampule (product)
  • Ibuprofen 5%/Levomenthol 3% gel (product)
  • Bone structure of head and/or neck (body structure)

A forward slash may be allowed in designations (non-FSN terms) in a variety of contexts. Some common examples of use are in acronyms with findings, and as an abbreviation meaning "and/or" concepts.


  • | O/E - abdominal mass palpated | Plus signs

For combination drug products, a "+" sign is allowed and should be used. Caret symbols (^)

As a workaround for the lack of markup that would allow proper representation of superscript characters, a pair of caret symbols is used to enclose character strings that properly should be displayed as superscript.


  • Technetium Tc^99c^ medronate (substance)
  • Blood group antigen Sd^a^ (substance)

Representing exponents: In alignment with the Unified Code for Units of Measure (UCUM) guidance on the use of powers of ten, the single caret is used to represent exponents, i.e. "powers of". For example, "10^3" for the third power of ten is acceptable. Pipe characters

SNOMED CT Compositional Grammar (SCG) syntax states that a term cannot contain a pipe character "|”.  Reason being that the pipe “|” is treated by SCG as the end of the term therefore use of this could cause confusion.