Dropping the hyphen from the adjective “radio-active”

“To hyphenate or not to hyphenate” [1] is a frequently occurring question in physics and chemistry. For example the term band gap can be found in the scientific literature printed in one word, bandgap, or in hyphenated form as band-gap.

What about the term radio-active? It first occurred in Pierre and Marie Curie's publication on July 18, 1898, in the Comptes Rendus de l'Academie des Sciences with the title “On a new radio-active substance contained in pitchblende,” announcing the isolation (discovery) of the element polonium. The Curies dropped the hyphen the following year [2]. Although the hyphenated form still appeared for some time, for example in treatises by Frederick Soddy and Ernest Rutherford, the non-hyphenated words radioactive and radioactivity eventually became standard forms.

If you happen to use a hyphen within these terms today, you should not be surprised when people assume that you are talking about something else, such as a radio station or electronic music: the German band Kraftwerk released a concept album with the title “Radio-Activity” (Radio-Aktivität in German) in 1975 [3].

References
[1] Karen Rieser: To Hyphenate or Not to Hyphenate. May 11, 2007 [http://www.suite101.com/content/to-hyphenate-or-not-to-hyphenate-a21048].
[2] Jean-Pierre Adloff: A Short History of Polonium and Radium. Chemistry International January-February 2011, 33 (1), pp. 20-23 [http://www.iupac.org/publications/ci/2011/3301/5_adloff.html].
[3]. Jason Ankeny: Radio-Activity, Review [http://www.allmusic.com/album/r11205].