a.

1. 雙重的；二倍的

n.

1. 【美】雙層樓公寓（每戶佔有上下兩層樓）；雙拼式房屋，聯式房屋（兩家合居，但各自分開）
2. 【電腦】雙工（一種雙向通信方式，通信雙方可同時進行信號的收、發動作）

n.

1. N. Amer. a residential building divided into two apartments.
   ▸a flat on two floors.
   ▸chiefly N. Amer. & Austral. a semi-detached house.
2. Biochemistry  a double-stranded polynucleotide molecule.

adj.

1. having two parts.
2. (of a printer) capable of printing on both sides of the paper.
3. allowing the transmission of two signals simultaneously in opposite directions.