Conditional Sentences

CONDITIONAL

Conditional tenses are used to speculate about what could happen, what might have happened, and what we wish would happen. In English, most sentences using the conditional contain the word if. Many conditional forms in English are used in sentences that include verbs in one of the past tenses. This usage is referred to as "the unreal past" because we use a past tense but we are not actually referring to something that happened in the past. There are five main ways of constructing conditional sentences in English. In all cases, these sentences are made up of an if clause and a main clause. In many negative conditional sentences, there is an equivalent sentence construction using "unless" instead of "if".

Conditional sentence type	Usage	If clause verb tense	Main clause verb tense
Zero	General truths	Simple present	Simple present
Type 1	A possible condition and its probable result	Simple present	Simple future
Type 2	A hypothetical condition and its probable result	Simple past	Present conditional or Present continuous conditional
Type 3	An unreal past condition and its probable result in the past	Past perfect	Perfect conditional
Mixed type	An unreal past condition and its probable result in the present	Past perfect	Present contditional

THE ZERO CONDITIONAL

The zero conditional is used for when the time being referred to is now or always and the situation is real and possible. 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.

If clause	Main clause
If + simple present	simple present
If this thing happens	that thing happens.
If you heat ice	it melts.
If it rains	the grass gets wet.

Read more about how to use the zero conditional.

TYPE 1 CONDITIONAL

The type 1 conditional is used to refer to the present or future where the situation is real. The type 1 conditional refers to a possible condition and its probable result. In these sentences the if clause is in the simple present, and the main clause is in the simple future.

If clause	Main clause
If + simple present	simple future
If this thing happens	that thing will happen.
If you don't hurry	you will miss the train.
If it rains today	you will get wet.

Read more about how to use the type 1 conditional.

TYPE 2 CONDITIONAL

The type 2 conditional is used to refer to a time that is now or any time, and a situation that is unreal. These sentences are not based on fact. The type 2 conditional is used to refer to a hypothetical condition and its probable result. In type 2 conditional sentences, the if clause uses the simple past, and the main clause uses the present conditional.

If clause	Main clause
If + simple past	present conditional or present continuous conditional
If this thing happened	that thing would happen. (but I'm not sure this thing will happen) OR that thing would be happening.
If you went to bed earlier	you would not be so tired.
If it rained	you would get wet.
If I spoke Italian	I would be working in Italy.

Read more about how to use the type 2 conditional with the present conditional and how to use the present continuous conditional in type 2 conditional sentence.

If clause	Main clause
If + simple past	present conditional or present continuous conditional
If this thing happened	that thing would happen. (but I'm not sure this thing will happen) OR that thing would be happening.
If you went to bed earlier	you would not be so tired.
If it rained	you would get wet.
If I spoke Italian	I would be working in Italy.

Read more about how to use the type 2 conditional with the present conditional and how to use the present continuous conditional in type 2 conditional sentence.

TYPE 3 CONDITIONAL

The type 3 conditional is used to refer to a time that is in the past, and a situation that is contrary to reality. The facts they are based on are the opposite of what is expressed. The type 3 conditional is used to refer to an unreal past condition and its probable past result. In type 3 conditional sentences, the if clause uses the past perfect, and the main clause uses the perfect conditional.

If clause	Main clause
If + past perfect	perfect conditional or perfect continuous conditional
If this thing had happened	that thing would have happened. (but neither of those things really happened) OR that thing would have been happening.
If you had studied harder	you would have passed the exam.
If it had rained	you would have gotten wet.
If I had accepted that promotion	I would have been working in Milan.

MIXED TYPE CONDITIONAL

The mixed type conditional is used to refer to a time that is in the past, and a situation that is ongoing into the present. The facts they are based on are the opposite of what is expressed. The mixed type conditional is used to refer to an unreal past condition and its probable result in the present. In mixed type conditional sentences, the if clause uses the past perfect, and the main clause uses the present conditional.

If clause	Main clause
If + past perfect or simple past	present conditional or perfect conditional
If this thing had happened	that thing would happen. (but this thing didn't happen so that thing isn't happening)
If I had worked harder at school	I would have a better job now.
If we had looked at the map	we wouldn't be lost.
If you weren't afraid of spiders	you would have picked it up and put it outside.

Conditional clauses without if

An example is given below.

If you invite her, she will come. (You have to invite her; otherwise she won’t come. Here the first thing you need to do is to invite her. If that does not happen, the second thing won’t happen either.)

We can also make conditional clauses without if.

Study the examples given below.

• If I had known his real motive, I wouldn’t have supported him.

We can express the same idea without if.

• Had I known his real motive, I wouldn’t have supported him.

Another example is given below.

• If I had realized the importance of physical training, I would not have wasted my time in front of the television.

source: http://www.ef.com/english-resources/english-grammar/conditional/
https://www.englishgrammar.org/conditional-clauses/

Active and Passive Voice

Active and Passive Voice

An action of a subject, in relation to an object, is expressed in two ways. These two ways of expressing action of a subject are known as Voices.

1. Active Voice

2. Passive Voice

Example.

·          I write a letter.                         (Active Voice)

·          A letter is written by me.      (Passive Voice)

The structure of same sentence changes when expressed as Active Voice or Passive Voice. The meaning of a sentence, either expressed as Active Voice or Passive Voice, remains the same.

·         Difference between Active Voice and Passive Voice.

The meaning or main idea of sentence, either expressed as Active Voice or Passive Voice does not change. The structure of a same sentence changes for Active Voice and Passive Voice.  We know that every sentence have a subject, a verb and an object. Subject is an agent who works on an object in a sentence. In the above example, “I” is the subject of the sentence that is doing some work on the object ‘letter’ in the same sentence.

To understand the difference in both voices, we should focus on the subject and the object of a sentence. In Active Voice, the subject acts upon the object. In Passive Voice, the object is acted upon by the subject. The meaning remains the same in both Voices but the sequence of the words (subject & object) changes. The sequence, of subject and object as in Active Voice, is reversed when it is expressed in Passive Voice. Read the following example for better understanding this difference.

 

The sequence of the subject and the object of the sentence is reversed while converting the sentence from Active Voice to Passive Voice.

The structures of a same sentence, for both Voices, are as follows:

 

·         Change in the Verb of a Sentence for changing Voice of a sentence

Apart from reversing the sequence of subject and object, the form of the verb of sentence also changes in both Voices. In the above example, you can see the change in the main verb as well as auxiliary verb of same sentence in both Voices. The only form of verb used in Passive Voice is the 3rd form of Verb which is also called Past Participle. Hence, the rule for changing verb for converting a sentence from Active Voice into Passive Voice is to use only 3rd form of Verb in Passive Voice. For changing the auxiliary verb for converting a sentence from Active Voice into Passive Voice, there are rules varying for tenses. To learn these rules, read the rules for Tenses as given in the links on this page. 

·         Basic Rules For Changing Active Voices Into Passive Voices

Rule No. 1. As mentioned earlier, the structure of sentence will be reversed in Passive Voice. The places of the Subject and the object will interchange. The subject will shift to the place of Object and the object will take the place of Subject in Passive Voice.

Rule No. 2. Only Past Participle Form or 3rd form of verb (e.g. eaten etc) will always be used as main verb in Passive voices for all tenses. No other form of verb will be used as main verb. It can be seen in all the examples given on this page.

Rule No. 3. The word “by” will be used before subject in the Passive voice.

Rule No. 4. Other words such as ‘with’ or ‘to’ may also be used instead of word ‘by’ depending upon the subject of the sentence. These words are used in a very few cases. The word ‘by’ is used in the most cases.

 

Rule No. 5. The auxiliary verb will be changed in Passive Voice depending upon the tense of sentence in its Active Voice. There are rules for changing the auxiliary for each tense which can also be studied on this website.

Rule No. 6. Subject may not be always mentioned in Passive Voice. A passive voice sentence can be written without having subject, if it gives clear idea about the subject. Read the following examples.

 

Note: The above rules, except rule No. 5, are the basic rules for changing Active Voices into Passive Voice and apply to all type of sentences. The rule No. 5 is about the usage of auxiliary verbs in Passive Voices which differs for each tense of the sentence. These rules for each tense have also been explained on this website.

source : http://www.studyandexam.com/active-passive-voice.html