Then and than are different words with different jobs. Then mainly relates to time and sequence, answering when or what happened next. Than is used for comparisons, showing difference between two things. Keeping the meaning in mind is the most reliable way to choose the correct word.

Then refers to time, order, or the next step in a process. Use then when you can replace it with at that time, next, or after that. It often connects events in a sequence and helps describe what happens in what order.

Than introduces the second part of a comparison. Use than when you are comparing two things and can rephrase the idea as compared with. It commonly appears after comparative adjectives and adverbs such as bigger, faster, and more.

Use then to talk about a moment in the past or future, or to show the next event in a timeline. It can appear at the beginning, middle, or end of a clause depending on emphasis. If the sentence is about when something happens, then is the correct choice.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use then for a specific time	🧠 对特定时间使用 then	Back then, we didn’t have smartphones.	📝 当时，我们没有智能手机。
Use then for the next step in order	🧠 按顺序的下一步使用 then	Finish your work, then call me.	📝 完成你的工作，然后给我打电话。
Use then meaning after that	🧠 表示在那之后使用 then	We ate dinner, then we watched a movie.	📝 我们吃完晚饭，然后看了一部电影。

Use than to link two sides of a comparison, especially after comparative forms like -er and more. It can compare people, objects, amounts, or actions. If the sentence answers which one is greater, smaller, faster, or more intense, than is the correct choice.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use than after comparative adjectives	🧠 在比较形容词之后使用 than	This road is narrower than the highway.	📝 这条路比高速公路窄。
Use than after comparative adverbs	🧠 在比较副词之后使用 than	She runs faster than I do.	📝 她跑得比我快。
Use than with more or less	🧠 与 more 或 less 搭配使用 than	I have less time than yesterday.	📝 我比昨天时间更少。

Then and than appear in predictable sentence patterns. Recognizing these patterns helps you choose quickly while reading and writing. Then often follows an instruction or marks a next action, while than follows a comparative word or phrase.

Word/Phrase	🇨🇳 中文 单词/短语	Definition	🇨🇳 中文 定义	Example	🇨🇳 中文 示例
if… then…	🧠 if… then…	result that follows a condition	📝 条件后跟随的结果	If it rains, then we’ll stay inside.	📝 If it rains, then we’ll stay inside.
now and then	🧠 now and then	occasionally	📝 偶尔	I go hiking now and then.	📝 我偶尔去远足。
more… than…	🧠 more… than…	comparison of degree	📝 程度的比较	It’s more complicated than it looks.	📝 它比看起来更复杂。
rather… than…	🧠 rather… than…	preference between two options	📝 两个选项之间的偏好	I’d rather walk than drive.	📝 我宁愿步行也不愿开车。

Then usually acts as an adverb that modifies when or in what order something happens. Than is typically a conjunction or preposition that introduces what you compare something to. Thinking about the role in the sentence can confirm the correct choice.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Then functions as a time or sequence adverb	🧠 Then 作为时间或序列副词	We’ll meet at six and eat then.	📝 我们六点见面，然后吃饭。
Than introduces the comparison target	🧠 Than 引入比较对象	The meeting was longer than expected.	📝 这次会议比预期的要长。
Then can connect two actions in one plan	🧠 Then 可以连接两个动作在一个计划中	Check the address, then send the package.	📝 核对地址，然后寄出包裹。

When you are unsure, replace the word with a short synonym to test the meaning. If next or after that fits, use then. If compared with fits, use than. This substitution test works in most everyday sentences.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Replace with next to check then	🧠 用 next 替换来检查 then	Read the email, then respond.	📝 读完邮件后再回复。
Replace with compared with to check than	🧠 用 compared with 替换来检查 than	This option is cheaper than the other one.	📝 这个选项比另一个便宜。
If both seem possible, focus on time vs comparison	🧠 如果两者都看起来可能，关注时间与比较之间的区别	Is it about when, or about which is more.	📝 它是关于何时，还是哪个更高/更多？

A simple memory aid is to connect the spelling to the meaning. Then contains e like event and time sequence, while than contains a like compare. This is not a grammar rule, but it can help you proofread quickly.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Then has e, think event order	🧠 Then 有 e，想到事件顺序	First we talk, then we decide.	📝 首先，我们谈话，然后再决定。
Than has a, think compare a to b	🧠 Than 含 a，想到用于比较	A is larger than B.	📝 A 比 B 大。

Use then for time, order, and what happens next. Use than for comparisons and differences between two things. If you check whether the sentence is about when or about comparing, you can choose correctly every time.