Expressing "be going to" with "yao"
The idea behind this usage of 要 (yào) is that someone is "planning to" or "going to" or "preparing to" do something. It's not that they just want to, or have to, it's that they fully expect to do it. It's in their plan.
This usage of 要 (yào) typically includes a time word of some sort, which may be placed before or after the subject.
Subj. + Time + 要 + Verb
Time + Subj. + 要 + Verb
- 我 明天 要 买 一 个 iPhone。 I am going to buy an iPhone tomorrow.
- 你们 现在 要 出去 吗？ Are you all going out now?
- 我们 今年 要 去 美国 。 We are planning to go to the U.S. this year.
- 他 下 个 月 要 来 中国 工作。 He is coming to China to work next month.
- 你 下 个 星期 要 去 她 家 吃 晚饭 吗？Are you going to her place for dinner next week?
- 这 个 星期天 你 要 做 什么？What are you doing this Sunday?
- 我 晚上 要 给 妈妈 打电话。 I am going to call my mom this evening.
- 下午 老师 要 来 我家。 The teacher is coming to my place this afternoon.
- 老板 明天 要 见 他们 吗？ Is the boss going to meet them tomorrow?
- 下班 以后 你 要 回家 吗？ Are you planning to go home after getting off work?
Sources and further reading
- 现代汉语八百词（增订本） (p. ) →buy
- Chinese Grammar - Broken down into 100 items - Basic and Intermediate Levels (汉语语法百项讲练 - 初中级)→buy