一直一个人英语可以说是"always alone"或"always by oneself"。"Alone"和"by oneself"都表示独自一人，只是前者比后者更强调孤独。这两个词都是由英语单词"alone"派生而来，"alone"本身的意思是独自的、孤独的、单独的。例如：

She's always been a bit of a loner, preferring to spend her time alone. (她一直有点孤僻，喜欢独自呆着。)

He's always been the type of person who enjoys spending time by himself. (他一直是那种喜欢独处的人。)

Despite having many friends, she still feels lonely and spends most of her time alone. (尽管有很多朋友，她仍然感到孤独，大部分时间都是独自一人。)