Is there any US/UK English difference in the spellings "birth weight" and "birthweight"? In scientific journals, I have found usage of both spellings.

E.g., Overall birth weight is not different for physically active women, though physical activity may reduce the risk for large-for-gestational age newborns.


As far as I can see, the correct usage is "birth weight" as two separate words, although the meaning of "birthweight" is immediately obvious and would be accepted by most people. This is an example of a compound word https://en.wikipedia.org/wiki/Compound_(linguistics), a phenomenon which is quite common when two words are repeatedly used together. Many English words are compound words: the process is that if the compound appears in print enough times it makes it into the dictionary and then it's "officially" a word.

As an aside, William Shakespeare gave a great number of words to the English language, and many of those are compound words. eg http://mentalfloss.com/article/48657/20-words-we-owe-william-shakespeare

  • But what if I have to cite an authority for word choice, and the document follows AmE? – Shaapj Mar 21 '16 at 13:52
  • You wouldn't normally have to cite an authority for the individual words in a paper, just the findings you refer to. What scenario are you worried about? When the person marking your paper says "Wait, shouldn't "birthweight" be a single word?"? This won't happen, but if it does, then at that point, you can say "Actually no, it's birth weight". In the same way, you don't need to provide a citation for every word you use, to prove it's spelled correctly. – Max Williams Mar 21 '16 at 14:49
  • I don't believe there's any difference between American and British English in this instance, either. "birthweight" isn't in the Merriam-Webster dictionary, which is my AmEng goto. – Max Williams Mar 21 '16 at 14:50

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