剣 by itself can be read either way. What's the difference?
Clarification: In particular, when 剣 refers to a 諸刃 sword, which reading are natives more likely to use?
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Sign up to join this communityA little research leads me to believe that つるぎ refers exclusively to double-bladed swords (諸刃{もろは}の剣{つるぎ}) while けん can refer to any sword, including single- or double-bladed, as well as a bunch of other metaphorical meanings and referring to sword arts and whatnot.
See the answer here:
http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1035588605
As for which is more common, it's けん.
tsurugi = native (ancient) Japanese word
ken = (ancient) Chinese pronunciation that came with Kanji
These two types of pronunciation are called 訓読み(和語) and 音読み(漢語)
We usually read 剣 as ken. tsurugi is not common.