A dress is always translated into 一条连衣裙, and in my opinion, a skirt is into 一条短裙. A dress一般指连身的套裙 or 晚礼服， but skirt is only wear on lower half of one's body. so, the right word for "a dress" in Chinese may be 一条连衣裙、一条裙子、一袭长裙、一身晚装......

连衣裙 = lián-yī-qún

dress 连衣裙 a woman's summer dress 女式夏装连衣裙

a woman's summer dress 女士夏季服飾 / 女性夏裝 (cf. 春裝 秋裝 冬裝)

裙子，短裙