What Do We Mean by 'Necessity'?
When we say 'necessity' we refer to something that needs to be done. In English, there are some words that help you give orders, whether to yourself or to others. Here are the words that are used to express necessity in English:
The modal verb 'must' can be used to express necessity and obligation. It expresses a strong obligation. It is mostly used in formal writings.
As you know, 'must' as a modal verb is followed by an infinitive without to (bare infinitive). 'Must' can refer to both present and future.
Using 'Have to'
Another way to express necessity and obligation is to use 'have to.' Using 'have to' is more common in English. And it is important to know that there is a bare infinitive used after have to.
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Actually, using 'have to' in interrogative sentences is very common. The only thing you have to be really cautious about is to use the auxiliary verbs (do, does, did), based on the tense of the interrogative sentences.
Using 'Have Got to'
One of the ways to express obligation and necessity is to use the phrase 'have got to'. This structure is actually more common in informal contexts or conversations. Remember, the verb after have got to must be a 'bare infinitive.'
As the verb 'have' in the phrase 'have got to' is an auxiliary, to make a question, all we have to do is to invert the subject and the auxiliary verb 'have.'
Using 'Need to'
The verb need can be used as either a helping verb or a main verb. In both cases, it can express necessity and obligation. Using the affirmative form of the helping verb 'need' is not common in English.
Grammarians tend to use the negative form though.
'Need' as a main verb is followed by a to-infinitive, but as a helping verb, it is followed by a 'bare infinitive.'
If we consider 'need' a main verb, as the general rule requires, we have to add the helping verbs (do, does, did) to the beginning of the sentence to make an interrogative sentence.
If we consider 'need' the helping verb, all we need to do is to follow the inversion rule and put the helping verb at the beginning of the sentence
'Shall' is a modal verb that can be used to describe formal obligation. By formal obligation, we mean 'documents' or 'official contexts.' This structure is normally used to give guidelines to people.
Since 'shall' is a modal verb making questions by it is too easy. All you need to do is to put the modal verb at the beginning of the sentence. In other words, you use the inversion and change the place of the modal verb and the subject.
What Is the Difference between 'Must' and 'Have to'?
Actually, both these terms are considered the same in speaking, but when it comes to rules and grammar, 'must' is used for internal necessity.
We mean things that you yourself chose to be an obligation for yourself unless we are talking about official documents or notices that are external obligations.
'Have to' is usually used for things that are externally necessary. It refers to rules and laws. In this case, orders that are expressed by 'have to' are really strict.
Necessity and Obligation: Past Tense
It is important to know that there is no past form for the modal verb 'must' in English. On the other hand, a past form for the phrase 'have got to' does not exist.
In this case, the past tense form for (have to, must, and have got to) is the phrase 'had to.'
'Should' is the past tense of the modal verb 'shall', but we cannot say that it functions exactly like the verb 'shall' in past form. Actually, 'should' can be also used to express 'obligation,' but this is usually the 'moral obligation' not something 'mandatory.'
If there is a strong obligation, you can use 'had to' instead of 'should'.
The past tense of the verb 'need' is 'needed' whether main verb or helping verb. And by all means, we use it to talk about past obligations. Remember, using 'need' as a helping verb in affirmative form is not common at all.
Anna and Pam
Using 'Not' after the Verbs
Among the verbs that we have mentioned, (shall, should, must, have got to, need) can be negated by adding the term 'not' to the auxiliary part of them. Check out the examples for clarification:
Negative Markers and Needn't
As you might know, 'negative markers' are not usually used with negative verbs, because they make 'double negation,' which is considered wrong in English grammar.
But when it comes to 'need not' grammarians tend to use 'negative markers' and it is surprisingly considered correct.
Using Helping Verbs
'Have to' and 'need' as the main verb need helping verbs [do, does, did] to be added by the term 'not' to make them negative. Here are some examples to be considered.
What Is the Difference between 'Must not' and 'Do Not Have to'?
- 'Must not' is used to indicate that something is important not to be done or happen.
- 'Do not have to' is used to refer to something that is not obligation or necessity, and it is optional for you to do it or not.
To Be Supposed to
'To be supposed to do something' is an expression that is used to say that we need to do something or something has to be done. To change the tense of the sentences you have to change the tense of the verb be. Check out the examples for clarification:
Using 'Had to Have'
You can use the past tense of have to (had to) before (have + past participle) To talk about things that needed to be done but in some cases, they may have happened or not. Check out the examples:
Using 'Should Have'
You can use the phrase 'should have' before 'past participles' to express things that were supposed to be done, but in some cases, they did not happen and now you somehow regret it.
There are some verbs and verb phrases that are used to talk about necessity. Here are the verbs.
- have to
- have got to
- need (to)
- What Do We Mean by 'Necessity'?
- What Is the Difference between 'Must' and 'Have to'?
- Needed (to)
- What Is the Difference between 'Must not' and 'Do Not Have to'?
- To Be Supposed to
- Using 'Had to Have'
- Using 'Should Have'