adverb, adverb taking the 'to' particle
gradually; little by little; more and more
Describes a gradual change over time; often used with verbs of change. The 'to' particle is optional and literary.
だんだん暖かくなってきた。
It's gradually getting warmer.
日本語がだんだん上手になった。
My Japanese has gradually improved.
As spring comes, it gradually gets warmer.
If you climb the steps of this shrine, you reach the top.
As I studied, I gradually started to understand Japanese.