質問: I've seen the phrase 1ターン1度 "once per turn" used in the Yu-Gi-Oh! Card game, so it seems like ターン is a legit counter. But I'm not sure how to pronounce it. From what I've googled so far, some people pronounce it like いったーん which is odd because ターン is a gairaigo. So how do you pronounce 1ターン?
回答: Both いちたーん and いったーん are valid. (As an aside, わんたーん is also very common, especially when it's part of a longer phrase like 1ターンキル.) There may be exceptions I'm not aware of, but basically foreign counters/units that start with K, T or P can be read both いち○○ and いっ○○. * 1カラット: いちからっと・いっからっと * 1キロ: いちきろ・いっきろ * 1テスラ: いちてすら・いってすら * 1トラック: いちとらっく・いっとらっく * 1トン: いちとん・いっとん * 1ペソ: いちぺそ・いっぺそ * 1ポンド: いちぽんど・いっぽんど