Question: In an essay I am writing, I am describing the handwriting of medieval Hebrew manuscripts from Spain. Should I use the descriptive term Sephardic or Sephardi? Likewise, in describing manuscripts from Germany would the appropriate term be Ashkenazi or Ashkenazic?
Answer: All four terms are used in scholarly books and journals when referring to Hebrew manuscripts.
The Oxford English Dictionary (online version accessed 22 February 2011) includes entries for both Ashkenazic and Sephardic, both as adjectives. There is an entry for Sephardi, but it is defined primarily as a noun, “A Spanish or Portuguese Jew” . There is no entry for Ashkenazi, although ironically OED uses this term in its definitions and etymologies of other entries!
Other English-language dictionaries include entries for all four terms.
The 2011 JTS Style Guide, issued by the JTS Communications Department, lists Ashkenazi and Sephardi in its section on transliterated words.
In short, if your editor requires all your terminology to be in the English language, I suggest you use Ashkenazic and Sephardic which have been fully incorporated into the English language as adjectives. Alternatively, if you have the option of using transliterated Hebrew words, you may prefer to use the terms Ashkenazi and Sephardi.