See, saw, seen are three forms of the same verb and they show time: present, past, and past participle. Use see for now and habits, saw for finished past time, and seen after auxiliary verbs like have or be. Choosing the right form depends on whether you are using a simple tense or a perfect or passive structure. Mastering these forms helps you speak and write with correct tense and grammar.

See is the base form and the present tense form used with I, you, we, and they. It also appears after modal verbs like can, will, should, and must, and after to in the infinitive. Use see when the action is general, habitual, or happening in the present depending on context and other words in the sentence.

In the simple present, see changes only in the third person singular: he, she, it. Most subjects use see, but he, she, and it take sees. This is about subject-verb agreement, not time, so it applies even when you talk about routines and facts.

Subject	🇨🇳 中文 主语	Form	🇨🇳 中文 形式	Example	🇨🇳 中文 例句
I	👤 我	see	✅ see	I see your point.	💬 我看到你的观点。
you	👤 你	see	✅ see	You see the problem.	💬 你看到这个问题。
he	👤 他	sees	✅ sees	He sees the sign.	💬 他看到标志。
she	👤 她	sees	✅ sees	She sees the difference.	💬 她看到差异。
it	👤 它	sees	✅ sees	It sees movement.	💬 它看见了移动。
we	👤 我们	see	✅ see	We see the results.	💬 我们看到结果。
they	👤 他们	see	✅ see	They see the change.	💬 他们看到变化。

Saw is the simple past form. Use saw for actions that happened and finished in the past, often with past time words like yesterday, last week, in 2020, or earlier. Saw does not change with the subject, so it is the same for I, you, he, she, it, we, and they.

Subject	🇨🇳 中文 主语	Form	🇨🇳 中文 形式	Example	🇨🇳 中文 例句
I	👤 我	saw	✅ saw	I saw her yesterday.	💬 我昨天看见了她。
you	👤 你	saw	✅ saw	You saw the notice.	💬 你看到了通知。
he	👤 他	saw	✅ saw	He saw the email.	💬 他看到了这封邮件。
she	👤 她	saw	✅ saw	She saw the show.	💬 她看到了这场表演。
it	👤 它	saw	✅ saw	It saw a shadow.	💬 它看见了一个影子。
we	👤 我们	saw	✅ saw	We saw the sunset.	💬 我们看到了日落。
they	👤 他们	saw	✅ saw	They saw the mistake.	💬 他们看到了这个错误。

Seen is the past participle form. You do not use seen alone as the main verb in standard English. Seen needs an auxiliary verb, most commonly have for perfect tenses or be for passive voice, to form a correct verb phrase.

Use have plus seen to talk about experience, completed actions with present relevance, or actions up to a time in the past. Choose have or has in the present perfect, and had in the past perfect. In these structures, seen never changes, only the auxiliary changes.

Subject	🇨🇳 中文 主语	Form	🇨🇳 中文 形式	Example	🇨🇳 中文 例句
I	👤 我	have seen	✅ have seen	I have seen that movie.	💬 我已经看过那部电影。
you	👤 你	have seen	✅ have seen	You have seen the report.	💬 你已经看过这份报告。
he	👤 他	has seen	✅ has seen	He has seen the update.	💬 他已经看过更新。
she	👤 她	has seen	✅ has seen	She has seen the message.	💬 她已经看过这条消息。
it	👤 它	has seen	✅ has seen	It has seen heavy use.	💬 它已经被广泛使用。
we	👤 我们	have seen	✅ have seen	We have seen improvement.	💬 我们已经看到改进。
they	👤 他们	have seen	✅ have seen	They have seen the changes.	💬 他们已经看到了变化。

Use be plus seen to focus on the thing that is observed instead of the person who observes. The auxiliary be changes for tense and agreement, while seen stays the same. This is common in formal writing, reports, and situations where the observer is unknown or unimportant.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use be plus seen for passive meaning	📌 使用 be 加 seen 来表示被动意义	The suspect was seen near the station.	📝 嫌疑人被看见在车站附近。
Change be for time and subject	📌 将 be 改变以表示时态和主语	The sign is seen from far away.	📝 从远处可以看到这个标志。
Add by to name the observer when needed	📌 在需要时添加 by 来指明观察者	The comet was seen by many people.	📝 这颗彗星被许多人看到。

In simple present and simple past, questions and negatives use do, does, or did plus the base form see. Do-support carries the tense, so the main verb stays see, not saw or seen. In perfect tenses, questions and negatives use have or has plus seen, not do-support.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Present questions use do or does plus see	📌 现在时疑问句用 do 或 does 加上 see	Do you see it.	📝 你看到它吗？
Present negatives use do not or does not plus see	📌 现在时否定句用 do not 或 does not 加上 see	She does not see the issue.	📝 她看不到这个问题。
Past questions use did plus see	📌 过去时疑问句用 did 加上 see	Did they see you.	📝 他们看到你了吗？
Past negatives use did not plus see	📌 过去时否定句用 did not 加上 see	I did not see it.	📝 我没有看到它。
Perfect questions use have or has plus seen	📌 完成时疑问句用 have 或 has 加上 seen	Have you seen my keys.	📝 你看到我的钥匙吗？
Perfect negatives use have not or has not plus seen	📌 完成时否定句用 have not 或 has not 加上 seen	He has not seen the email.	📝 他没有看到这封邮件。

These forms appear in very common structures that signal which form to choose. After modals, use see. After have, use seen. For reported observations in the past, saw is common with a finished time reference. Learning these patterns helps you choose quickly without translating.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
After modals use see	📌 模态动词后使用 see	I can see the answer now.	💬 我现在能看到答案。
After to use see	📌 在 to 之后使用 see	I want to see it again.	💬 我想再看一次它。
After have use seen	📌 have 之后使用 seen	We have seen enough.	💬 我们已经看到了足够的。
Finished past time uses saw	📌 完成过去时使用 saw	We saw it last night.	💬 我们昨晚看到了它。

In some dialects and informal speech, people may say seen as a simple past form, like I seen it. In standard written English and most formal spoken English, this is considered incorrect. For standard usage, use saw for the simple past and reserve seen for structures with have or be.