The buyer has to sign a delivery note as proof of receipt.

购买者必须签收送货单表明货已收到。

《牛津词典》

World leaders are expected to sign a treaty pledging to increase environmental protection.

人们期望世界领导人们能签署一份承诺加强环境保护的条约。

《柯林斯英汉双解大词典》

Here at the Sea Life Centre we're taking action by asking as many people as possible to sign a petition.

在海洋生物中心，我们正在采取行动，请求尽可能多的人签署一份请愿书。

youdao

(TRANSLATION) "It is a clear sign that the United States is taking Russia and its arguments as seriously as their national security considerations."

VOA: standard.2009.09.17

Marketers buy the ads and then figure out their return on investment based on how many people click on them, "like" them (remember the value of a "like") or take some other action (sign up for a contest, download, etc.).

FORBES

That's a good sign. (Applause.) That's a good sign.

WHITEHOUSE: President Obama Tells Wall Street to Back Reform

You can sign-up (or sign-off) on a monthly basis throughout the year.

FORBES: Are High Gas Prices Leaving You "Gas"-ping for Relief?