どんどんProgressively, Rapidly increasing, More and more

どんどん (or ドンドン) is one of the countless words in Japanese that represent a particular sound or sensation. These words are known as onomatopoeia (オノマトペ in Japanese). どんどん represents the sound of banging (like on a drum), or the pounding of feet. In this way, it is regularly translated as 'rapidly', or 'quickly'.

Like だんだん, どんどん may be used before almost any phrase.

While どんどん can take the particle と, it is not required. In fact, と is very often omitted from adverbs/onomatopoeic words in Japanese.

Caution

Initially, it can be easy to mix-up どんどん, with だんだん. だんだん is used to express slower changes, and may be thought of as similar to 'steadily', or 'step by step' in English.

Fun Fact

When the と particle is used with onomatopoeic words, it is very similar to one of と's main usages as a quotation marker in Japanese. This means that と has a similar role to words like 'went', or 'goes' in English. For example, In English, we would say:

The door 'goes' BANG with the wind.

However, the door doesn't actually 'go' anywhere. This is similar to what と is doing here.