along可作介词,也可作副词。
作介词时表示“沿着……”:
He walked along Oxford Street. 他沿牛津街走着。
也可表示“在……旁边”:
His office is along the corridor. 他的办公室在走廊旁边。
作副词时它表示:
向前:
He whistled as he walked along . 他一面往前走,一面吹着口哨。
和……一道:
She was willing to take him along . 她愿意带着他(一道)。