spontaneously [spɑːn'teɪnɪəslɪ]

用法：副词，表示自发地、自然地、无意识地。

例句：

1. The children spontaneously burst into laughter when they saw the clown.

孩子们看到小丑时自然而然地笑了起来。

2. The flowers in the garden grew spontaneously without any human intervention.

花园里的花自然生长，没有任何人为干预。

3. He spontaneously offered to help his neighbor carry the heavy groceries.

他主动提出帮助邻居搬运沉重的杂货。

4. The audience was moved to tears when the singer spontaneously dedicated a song to his late mother.

歌手自发地把一首歌献给已故的母亲，观众被感动得热泪盈眶。

5. The idea for the new product came to her spontaneously while she was taking a shower.

她在洗澡时突然想到了新产品的构思。

同义词及用法：

1. voluntarily (adv.) 自愿地，主动地

2. instinctively (adv.) 本能地，天性地

3. unconsciously (adv.) 无意识地，不知不觉间

4. impulsively (adv.) 冲动地，莽撞地

编辑总结：

spontaneously是一个表示自发、自然、无意识的副词。它可以用来描述人们做出的行为或反应，也可以用来形容事物的发展或变化。它的同义词包括voluntarily、instinctively、unconsciously和impulsively，但每个词都有着不同的侧重点。在使用时，需要根据具体语境选择合适的词汇。