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Annette Flanagin


Italics is a form of roman type style that slants to the right. Italics have multiple uses. However, setting large blocks of body text in italics should be avoided because legibility is reduced. Use italics as follows:

  • For level 4 heads (second-level side heads)

  • When terms are described as terms, and letters as letters (see also 8.6.7, Punctuation, Quotation Marks, Coined Words, Slang, and 8.7.5, Punctuation, Apostrophe, Using Apostrophes to Form Plurals):

    The page number is called the folio.

    In his handwriting the n’s look like u's.

  • For titles of books and journals, proceedings, symposia, plays, paintings, long poems, musical compositions, space vehicles, planes, and ships (see also 10.2, Capitalization, Titles and Headings):

    Archives of General Psychiatry

    USS Constitution

    Verdi’s Requiem

  • For epigraphs set at the beginning of a work (see the beginning of this chapter).

  • For some non-English words and phrases (see also 12.2, Non-English Words, Phrases, and Accent Marks, Accent Marks [Diacritics]) that are not shown among English terms in the current edition of Merriam-Webster’s Collegiate Dictionary or in accepted medical dictionaries. Italics are not used if words or phrases are considered to have become part of the English language, eg, café au lait, in vivo, in vitro, en bloc.

  • For lowercase letters used in alphabetic enumerations of items or topics (the parentheses are set roman): (a), (b), (c), etc.

  • For genus and species names of some microorganisms, plants, and animals when used in the singular and the names of a variety or subspecies. Plurals, adjectival forms, taxa above genus (eg, class, order, family) are not italicized (see also 15.14, Nomenclature, Organisms and Pathogens):


    Staphylococcus aureus




    Streptococcus (But: organisms, streptococcal, streptococci)

  • For portions of restriction enzyme terms (see also 15.6.1, Nomenclature, Genetics, Nucleic Acids and Amino Acids)

  • For gene symbols but not gene names (see also 15.6.2, Nomenclature, Genetics, Human Gene Nomenclature; 15.6.3, Nomenclature, Genetics, Oncogenes and Tumor Suppressor Genes; and 15.6.5, Nomenclature, Genetics, Nonhuman Genetic Terms)

  • For chemical prefixes (N-, cis-, trans-, p-, etc) (see also 15.4.4, Nomenclature, Drugs, Chemical Names, and 15.10, Nomenclature, Molecular Medicine)

  • For mathematical expressions such as lines, variables, unknown quantities, and constants (see also 21.0, Mathematical Composition). Numerals or abbreviations for trigonometric functions and differentials are not italicized:

    sin x = a/b

  • For some statistical terms (see also 20.10, Study Design and Statistics, Statistical Symbols and Abbreviations):







  • For the abbreviation for acceleration due to gravity, g, to distinguish it from g for gram (see also 14.11, Abbreviations, Clinical, Technical, and Other Common Terms)

  • For legal cases (see also 3.16, References, US Legal References), eg, Roe v Wade

  • For the term sic (see also Insertions in Quotations in 8.5.2, Punctuation, Parentheses and Brackets, Brackets)

  • In formal resolutions, for Resolved

  • Sparingly, for emphasis

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