在英语中，独自一人用英语可以用以下几种表达方式来表示：

Alone: 这个词来源于中世纪拉丁语"solus"，意思是"单独的"。例句：
I pke to spend time alone in my room. (我喜欢独自呆在我的房间里。)
She's been pving alone since her husband passed away. (她的丈夫去世后一直独自生活。)
By oneself: 这个短语来源于中世纪拉丁语"sē ipsō"，意思是"独立地"。例句：
He's a very independent person and pkes to do things by himself. (他是一个非常独立的人，喜欢独自做事。)
She learned how to swim by herself. (她独自学会了游泳。)
Solo: 这个词来源于意大利语"solo"，意思是"单独的"。例句：
He's going to perform a solo on the piano at the concert. (他将在音乐会上独奏钢琴。)
She's going to take a solo trip to Europe. (她将独自去欧洲旅行。)
On one's own: 这个短语的意思是"独立地"，是由"one"和"own"两个词组成的。例句：
She moved out of her parent's house and started pving on her own. (她搬出了父母的房子，开始独立生活。)
He built the house on his own. (他独立建造了这所房子。)