因故不能赴约的道歉信英语作文需包含以下核心要素：表示歉意、说明原因、提出解决方案。以下是综合权威信息整理的范文及要点：

一、基本结构与要点

1. 开头致歉

   使用"Sorry"开头，直接表达歉意，例如："I'm sorry to inform you..."。

2. 说明原因

   简洁说明无法赴约的具体原因，如考试、突发状况等，避免冗长。例如："Due to an important exam coming up..."。

3. 提出解决方案

   另约时间或说明替代方案，体现诚意。例如："Would you be available next Saturday？"。

二、范文参考

1. 考试冲突类

   Dear Anne, Thank you for your invitation to your family tomorrow evening. Unfortunately, I regret that I cannot join you because I have an important exam coming up. I hope you enjoy the gathering and feel free to contact me later. Best regards, Li Hua.

2. 突发状况类

   Dear Miss Nancy, I regret to inform you that I couldn't keep my promise to attend your birthday party last Saturday. My son fell ill early, and I had to take care of him. I hope to see you soon. Truly yours, Tom.

3. 行程变更类

   Dear Tom, I'm very sorry that I can't go on the trip to Beijing with you next weekend. My cousin Li Ming is returning from abroad, and I need to pick him up at the airport. I hope you understand and accept my apologies. We can plan another time later.

三、注意事项

• 语言简洁 ：避免使用复杂句式，保持100-150字即可。

• 态度诚恳 ：用"regret"、"apologize"等词汇表达歉意。

• 提供替代方案 ：增加接受度，避免单方面拒绝。

以上内容综合了权威信源的实用模板，可根据具体场景调整细节。