Up regulation, upregulation or up-regulation? Rules of hyphenation

October 22, 2015

Dr. Jennifer C van Velkinburgh, Filipodia Publishing


Prefixes that can stand alone as words (such as cross, half, and all) require hyphenation when used as adjectives; for example, cross-section, half-life, and all-inclusive. Exceptions to this rule include some commonly unhyphenated words, such as outpatient and overexposed. Prefixes attached to a word or phrase starting with a capital letter (such as anti-HLA and non-Euclidean) should be hyphenated.


Prefixes that cannot stand alone as words (such as anti, bi, co, hyper, hypo, infra, inter, intra, micro, multi, peri, pre, pseudo, re, sub, supra, ultra) are not be hyphenated when used as adjectives; for example, antimicrobial, biannual, cotransfection, hypervascular, and infrared. However, when these prefixes are used with two vowels or the same consonants abutting (such as hyper-reactive, pre-operative, anti-inflammatory, co-infection), then the term should be hyphenated.


Therefore, following English grammar rules, the correct presentation for direction of ‘regulation’ requires hyphenation.

Correct: up-regulation, down-regulation

Incorrect: up regulation, upregulation, down regulation, downregulation


Moreover, the Medical Subject Headings (known as MeSH terms), which are the controlled vocabulary used for indexing journals (such as in MEDLINE/PubMed database), use the proper English grammar rules for hyphenating these two terms. Please query https://www.nlm.nih.gov/mesh/2015/mesh_browser/MBrowser.html to see the MeSH terms for directional regulation as ‘up-regulation’ and ‘down-regulation’.


Follow up or follow-up?


In general, when the term is used as a noun (person, place, thing) or an adjective (qualifier/modifier of a noun or pronoun), it should be hyphenated (such as “follow-up”); when it is used as a verb (action, occurrence), it should not be hyphenated and should be written as two separate words (such as “follow up”). Therefore, when the term “follow-up” is used as a heading for a sub-section it should be hyphenated.