The noun 订单 (dìngdān) means 'order' in a commercial sense, referring to a formal request to purchase goods or services. It is widely used in business and trade contexts. For example, 交易订单 means 'trade orders.'
我昨天在网上下了一个订单。
Wǒ zuótiān zài wǎngshàng xià le yí ge dìngdān.
Yesterday I placed an order online.
公司今天收到了三百多个订单。
Gōngsī jīntiān shōudào le sānbǎi duō ge dìngdān.
The company received over three hundred orders today.
你的订单预计下周送达。
Nǐ de dìngdān yùjì xià zhōu sòng dá.
Your order is expected to arrive next week.