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Should the word be written as X-ray or x-ray?

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Let's throw the hyphen into the debate. As a legal transcriptionist, I rely on Merriam Webster's Legal Speller. It shows x-ray as a verb, and X ray as a noun. – user10358 Jun 27 '11 at 4:42

4 Answers

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Wikipedia capitalizes the X. Wiktionary says that x-ray is the alternative spelling of X-ray, not the other way round. Merriam-Webster capitalizes the noun but not the verb, noting that the verb is "often capitalized", too.

Looking through the first 250 cites in the Corpus of Contemporary American English, the capitalized version is preferred by a factor of 2:1; looking through the first 250 cites in the British National Corpus, it wins by a factor of 11:1.

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+1 for a great answer. Much more comprehensive than mine. – Tragicomic Jan 25 '11 at 9:58
I am assuming the British know their language then and will switch to X-ray. – Johan Jan 25 '11 at 10:07
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When used as a noun or a modifier, the "X" in X-ray is capitalized.

  • The doctor looked at the patient's X-ray.
  • Do you think all superheroes have X-ray vision?

When it is used as a verb, the "X" is usually capitalized.

  • Your chest needs to be X-rayed.

However, the entry on Merriam Webster Online for X-ray as a verb lists it with a small "X". It does say, though, that the verb is often capitalized.

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Yeah, I've definitely seen uses of both X-ray and x-ray. But the capitalized version is more common? – Johan Jan 25 '11 at 9:37
OED online has only the capitalized spelling. The only reference I could find to the lowercase x-ray was in Merriam Webster Online, and only when it is a verb. It is capitalized whenever it is used as a noun. oxforddictionaries.com/view/entry/m_en_gb0964080#m_en_gb0964080 – Tragicomic Jan 25 '11 at 9:46
The NOAD reports that you can write X-ray, x-ray, or X ray, but the entry in the dictionary is for X-ray. – kiamlaluno Jan 26 '11 at 12:54
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I work on veterinary journals and our go-to dictionaries are Dorland's Illustrated Medical Dictionary (30th Ed.) and Saunders Comprehensive Veterinary Dictionary (2nd Ed.) Neither of these capitalizes x-ray (as a verb or a noun), and both dictionaries show that a hyphen is used.

I am not sure where the OP is using the term, but it seems that in medical literature the word radiograph is preferred over x-ray. Also, our authors rarely, if ever, use x-ray as a verb.

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So what do they use as a verb? "Radiographing"? – Johan Apr 1 '12 at 14:24
They use radiograph as the verb. "We radiographed the dog's leg." Or they say they "perform radiography." – JLG Apr 1 '12 at 14:51
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According to the Chicago Manual of Style, 16th edition, x-ray is not capitalized. Not when it's a noun, a verb, or an adjective. This is the standard for fiction writing.

I am both a speech-language pathologist and a fiction writer.

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