プログレッシブ和英中辞典(第4版)の解説
みっか【三日】
〔３日間〕(for) three days
三日目
the third day
三日とあげず
very often／almost every other day
三日おきに
every fourth day／every four days
三日天下
a short-lived reign
三日坊主
彼は三日坊主だ
He can't stick to anything.／He can't keep his resolutions longer than a day or two.