动词不定式的形式

动词不定式是一种非限定性动词形式，通常由“to”加上动词原形构成，如“to run”或“to eat”。它在句子中可以承担除谓语之外的任何成分，如主语、宾语、补语等。动词不定式的否定形式是在“to”前面加上“not”，如“not to run”或“not to eat”。动词不定式有三种形式：基本形式、进行形式和完成形式。基本形式是“to”加上动词原形，进行形式是“to be + 动词的现在分词”，完成形式是“to have + 动词的过去分词”。动词不定式还可以有被动语态形式，基本形式是“to be + 动词的过去分词”，进行形式是“to be + 动词的现在分词的被动语态”，完成形式是“to have been + 动词的过去分词”。动词不定式在句子中的作用非常多样，可以用来表示目的、原因、结果、条件等。例如，“I want to go to the store”（我想去商店）中的“to go”表示目的，“He went to the store to buy milk”（他去商店买牛奶）中的“to buy”表示目的，“She is too tired to run”（她太累了，不能跑步）中的“to run”表示结果。

Infinitives, a type of non-finite verb form, are integral to English grammar. They are characterized by their lack of conjugation, which means they do not change to reflect person, number, or tense. This lack of inflection is what gives them their name, as they are not "defined" by these grammatical features. Infinitives are classified as non-finite verb forms.

Forms of the Infinitive

Infinitives can take on several forms, each with its own specific use and meaning:

1. The Simple Form

The simple form of the infinitive is used to express actions that occur simultaneously with, or after, the action of the main verb. It is typically structured as "verb + to + base form of the verb":

Example: "He seems to know this."

Example: "I hope to see you again," which can also be expressed as "I hope that I'll see you again."

2. The Perfect Form

The perfect form indicates an action that has been completed before the action of the main verb. It is formed by adding "to have" followed by the past participle of the verb:

Example: "I'm sorry to have given you so much trouble."

Example: "He seems to have caught a cold."

3. The Progressive Form

The progressive form is used to describe an action that is ongoing at the same time as the action of the main verb. It is constructed by using "to be" followed by the present participle (-ing form) of the verb:

Example: "He seems to be eating something."

4. The Perfect Progressive Form

The perfect progressive form is used to indicate an action that has been ongoing for a continuous period up to the point of the main verb's action. It is formed by adding "to have been" followed by the present participle of the verb:

Example: "She is known to have been working on the problem for many years."

Future Actions with Infinitives

Infinitives can also be used to express future actions, especially after verbs that convey emotions or intentions. This is done by adding "to" followed by the base form of the verb:

Example: "I plan to visit the museum next week."

Understanding and correctly using infinitives is crucial for mastering English grammar and enhancing the expressiveness of one's speech and writing.