however与especially

however用在句首，句中都可以，

especially通常只能用在句中

however [简明英汉词典]

[hau5evE]

adv.无论如何, 可是, 仍然, 究竟

conj.不管用何种方法, 然而, 可是

especially [简明英汉词典]

[is5peFEli]

adv.特别, 尤其