Present Perfect Tense

past perfect

When the main clause is in the past or past perfect tense, the subordinate clause must be in the past or past perfect tense. He said that he wanted to go. (NOT He said that he wants to go.) (Here the main clause (He said) is in the simple past tense and hence the subordinate clause, too, should be in the past tense.)

present tense

These two actions (“stood” and “waved”) happen at the same time and hence, need to have the same tense. This sentence could take place in the present or future tense too, but both verbs will still need to take on the same tense. For example: Example 2: During my matches, my dad stands up and waves at me.

The zero conditional is often used to refer to general truths. The tense in both parts of the sentence is the simple present. In zero conditional sentences, the word “if” can usually be replaced by the word “when” without changing the meaning….The zero conditional.

Conditional Sentences are also known as Conditional Clauses or If Clauses. They are used to express that the action in the main clause (without if) can only take place if a certain condition (in the clause with if) is fulfilled.

The short answer is no, but there are exceptions to the rule. An if- or when-clause (often used to form conditional sentences) generally does not contain “will,” which is the simple future tense of the verb “to be.” One exception is when the action in the if- or when-clause takes place after that in the main clause.

We can use if to combine two clauses. Study the example given below….

1. If he wants to pass the test, he has to work harder.
2. If you meet him, ask him to come over here.
3. If you work hard, you will get good marks.
4. If you invite her, she will come.
5. If you do not obey the rules, you will be persecuted.

To combine two independent clauses (complete sentences), use a semicolon or a comma and conjunction. To attach a dependent clause, use a comma if it comes before the independent clause; use no comma if it comes after the independent clause, unless it is a “contrast word” (although, though, even though, whereas).

Combine using unless

1. Unless means if not.
2. Unless you work hard, you cannot win.
3. Unless the boys work hard, they will fail.
4. Unless you start early, you will get stuck in the traffic.
5. Unless you hire a taxi, you will miss the train.
6. Unless you obey my orders, you will be dismissed.

Unless means the same as if…not. Like if, unless is followed by a present tense, a past tense, or a past perfect tense (never by a conditional). Unless is used instead of if…not in conditional sentences of all types. The order of the clauses doesn’t matter with sentences using unless.

As you probably already know, “if” is conditional. It is used to describe a possible situation, and what would happen under the conditions of that situation. “Unless” is also conditional, but it is effectively “if” with an extra exclusion or negative qualifier added. Unless basically means “except if” or “if… not”.

Using Unless

1. Present. You will damage your health unless you stop smoking. = you will damage your health if you do not stop smoking.
2. Past. Unless she was working late, she would be here. = If she was not working, she would would be here.
3. Past Perfect. I wouldn’t have taken Paul unless his car hadn’t broken down.

I can’t refund you your money until and unless you send me original receipts. I can’t start work on this project unless and until the plans are approved. Note that present tenses are used with both until and unless to indicate future time.

Complex Sentences with “unless” A complex sentence with “unless” contains at least one independent clause and at least one dependent clause. Dependent clauses can refer to the subject (who, which) the sequence/time (since, while), or the causal elements (because, if) of the independent clause.

The word “unless” can serve as a connector, as in Model Sentence 1, or it can come at the beginning, as in Model Sentence 2. “Unless” must go directly with the condition. If the condition and “unless” are separated, it sounds quite strange.

conjunction

Unless means something similar to ‘if … not’ or ‘except if’. … We use the conjunction unless to mean ‘except if’. The clause which follows unless is a subordinate clause (sc): it needs a main clause (mc) to make a complete sentence. …

We use the conjunction unless to mean ‘except if’. The clause which follows unless is a subordinate clause (sc): it needs a main clause (mc) to make a complete sentence. When unless comes before the main clause, we use a comma: Unless [SC]it rains, [MC]we’ll go for a picnic by the river tomorrow.

Dependent clauses almost never require commas unless there is something else in the sentence making you use one. Because ‘unless’ can only be used at the start of a dependent clause, this means you will almost never need a comma before ‘unless. ‘

The easiest way to explain “unless” is to say it is the equivalent of a negative if-clause. If I do NOT win the lottery, I will not be able to buy a car. Unless I win the lottery, I will not be able to buy a car.

Often when we are talking about present situations, we use unless instead of if…not. Unless means except if or simply it means if…not. Both of these examples have the same meaning and refer to the present time. “You can’t go on vacation unless you save some money.”

IF. An if phrase expresses that one action or situation must happen first before the other one will/can happen. The action in the clause following if expresses either: (1) a condition for a singular outcome to occur; or (2) a recurring situation “whenever” with a predictable outcome (in general).

At least means like “the lowest in importance or rank” and unless is like “except for …”

1 : a group of words containing a subject and predicate and functioning as a member of a complex (see complex entry 2 sense 1b(2)) or compound (see compound entry 2 sense 3b) sentence The sentence “When it rained they went inside” consists of two clauses: “when it rained” and “they went inside.”

There are two types of clause:

• An independent clause (one that can stand alone as a sentence).
• A dependent clause (one that is usually a supporting part of a sentence).