渐渐 "gradually"
The adverb 渐渐 
indicates that an action or a change takes place in a slow and gradual manner.
渐渐 is placed before a predicate. The particle 地 is often placed between 渐渐 and the predicate.
indicates that an action or a change takes place in a slow and gradual manner.
渐渐 is placed before a predicate. The particle 地 is often placed between 渐渐 and the predicate. Pay attention
渐渐 can only be used in declarative sentences.
Examples
他渐渐明白了妈妈为什么这样说
Gradually, he realized why his mother had said that (he hadn’t realized before)
tā jiànjiàn míngbái le māma wèishénme zhèyàng shuō
刚来中国我不会用筷子，但是后来渐渐地会用了
I couldn't use chopsticks when I first came to China, but later I learned how to use them
gāng lái zhōngguó wǒ bú huì yòng kuàizi, dànshì hòulái jiànjiàn de huì yòng le
渐渐地 can be placed at the beginning of a sentence and separated by a comma. However, the meaning doesn't change.
Let's compare:
Examples
渐渐地，天黑了
It was getting darker
jiànjiàn de, tiān hēi le
天渐渐地黑了
It was getting darker
tiān jiànjiàn de hēi le