Special is more common than especial, which has the same meaning; but especially is for rhythmical reasons (because it occurs most frequently at the beginning of a dependent clause, where usually an unaccented particle occurs, and where, therefore, a word with an accent on the first syllable is instinctively avoided) much more common than specially. [Century Dictionary]
Special 比 especial 更常見,意思相同; 但是,由於韻律原因(因爲它最常出現在從屬從句的開頭,通常會出現一個非重音粒子,在那裏,因此,本能地避免使用一個重音在第一個音節上的單詞), especially 比 specially 更常見。[世紀詞典]