A prefix used to add emphasis meaning 'very, foremost, earliest' as in compounds like 'いち早く' or 'いちおし.'
新商品はメディアでいち早く紹介された。
The new product was introduced in the media very early.
この店のいちおしメニューは唐揚げだ。
The shop's top recommended menu item is karaage (fried chicken).
いち早く行動することが大事だ。
It's important to act as quickly as possible.