If I have time next week, I will go with you.
The teacher suggested that we clean the blackboard at last.
Subjunctive mood is a difficult grammatical problem. However, as long as you summarize the composition and usage of subjunctive mood, you can easily get it. The usage of subjunctive mood can be summarized as follows:
The usage of 1. subjunctive mood in conditional sentences
(1) If the assumption is contrary to the present fact, use the past tense in the conditional sentence and the past future tense (should, should, would, main verb prototype) in the main sentence; If it means that something is unlikely to be realized in the future, you can also use "we to+ verb prototype" or past tense verbs in conditional clauses. For example:
If I have time, I will definitely go. (now)
In case it rains, we won't go out.
If I knew German, I would read this paper to you ... (now)
If he were here, we could ask him ... (now)
(2) If the assumption is contrary to the past facts, use the past perfect tense in the clause and the past perfect tense (should, would, could, may+have+ past participle) in the main sentence. For example:
If I had started earlier, I would have caught the train.
If she were not so busy, she might come.
If I hadn't taken your advice, I would have made a serious mistake.
If only you hadn't told him the news.
(3) In the conditional adverbial clause with subjunctive mood, if there are three words, if can be omitted in formal language or written language, and then the subject and predicate verbs of the sentence are all inverted or partially inverted. For example:
If they have time, they will certainly come to help us.
If the weather is fine, we will go for an outing.
If I go, I will go.
(4) If the time referred to in the main clause is inconsistent, that is, the conditional clause indicates that it is contrary to the past facts, and the main clause indicates that it is contrary to the present facts; Or the conditional sentence means the opposite of the present fact, and the main sentence means the real situation, then the subjunctive form corresponding to the specific time should be adopted in the clause. For example:
If it rained last night, it would be very cold today.
If I had taken your advice, I wouldn't have any difficulty in my work now.
2. The usage of subjunctive mood in object clauses
In the object clause, the verbs suggest, command, demand, proposal, request, command, insist, etc. The subjunctive mood (that is, Should+ verb prototype or only verb prototype) is used to express wishes, suggestions, commands, requests, etc. In the object clause after the verb wish/ would rather, the past tense is used to indicate that it is inconsistent with the present facts, and the past perfect tense is used to indicate that it is inconsistent with the past facts. For example:
I suggest that we start at once.
The doctor insisted that the patient undergo an X-ray examination.
I wish I were as strong as you.
I'd rather you didn't tell him.
3. The usage of subjunctive mood in the subject clause
In it is necessary/important/strange/natural; Requests/suggestions/expectations/proposals; The subjunctive mood should be used in the subject clause after the structure of pity, that is, the prototype of Should+ verb or the prototype of only verb. For example:
It is necessary to send him there at once.
Professor Li was asked to give us a speech.
I hope we can get everything ready before tonight.
4. The usage of subjunctive mood in predicative clauses and appositive clauses.
Use subjunctive mood in predicative clauses and appositive clauses after nouns such as suggestions, suggestions, ideas, plans, orders and advice, that is, should+ verb prototype or only verb prototype. For example:
Our suggestion is that you go first.
My suggestion is that we should ask Dr. Li.
Do you know the orders you should obey?
5. The usage of subjunctive mood in other adverbial clauses
In the adverbial clause guided by if, the past tense is used to indicate that it is inconsistent with the present facts, and the past perfect tense is used to indicate that it is inconsistent with the past facts; In the adverbial clause guided by so that, the prototype of the verb should/would/could/may+ is often used to express the subjunctive mood for that. For example:
They talked as if they had been friends for years.
She stayed at home for a few days so that she could take care of her mother.
He took a taxi to the station so that she wouldn't miss the train.
6. The usage of subjunctive mood in attributive clauses:
In the attributive clause after it is time, the past tense is often used to express virtuality.