早速(さっそく)at once, immediately, without delay, promptly

メールを送(おく)った。早速(さっそく)返事(へんじ)が来(き)た。

I sent an email. I got a reply immediately. {at once, immediately, without delay, promptly}

部長(ぶちょう)：「早速(さっそく)、仕事(しごと)に取(と)り掛(か)かろう！」

Department Head: 'Let's get to work right away!' {at once, immediately, without delay, promptly}

メール：「早速(さっそく)のお返事(へんじ)を有難(ありがと)う御座(ござ)います。」

Email: 'Thank you for your prompt reply.' {at once, immediately, without delay, promptly}

取引(とりひき)先(さき)：「早速(さっそく)ですが、取引(とりひき)の話(はなし)を中心(ちゅうしん)に話(はな)し合(あ)いを始(はじ)めましょう。」

Client: 'Without further ado, let's start discussing mainly about the business deal.' {at once, immediately, without delay, promptly}

電話(でんわ)をしたら早速(さっそく)出(で)てくれた。どうやら暇(ひま)を持(も)て余(あま)していたようだ。

When I called, they immediately answered. It seems they had some free time on their hands. {at once, immediately, without delay, promptly}