1. altern- + -ate + -ly.
2. => one after the other, by turns.
3. Alternate means "by turns;" alternative means "offering a choice." Both imply two kinds or things.
英文词源
alternately (adv.)
early 15c., from alternate (adj.) + -ly (2).
双语例句
1. He could alternately bully and charm people.
他一会儿欺负人一会儿取悦人。
来自柯林斯例句
2. She became alternately angry and calm.
她时而愤怒时而平静。
来自柯林斯例句
3. This movie is by turn ( = alternately ) terrifying and very funny.