Difference Between Could and Should

The English language is one of the most widely used languages around the globe.

Some words can be used interchangeably as they are slightly different, and the difference is figured out by experts, but it seems similar to people when used on a daily basis.

Auxiliary verb, also known as helping verb, is used along with the main verb to help express the main verb’s mood, tense, and voice. Some of the examples of an auxiliary verb are could, would, should, might, to be, to have, etc.

Could vs Should 

The main difference between Could and Should is that could is used to say about something or some action or event that is possible or has a great possibility of happening.

In contrast, ‘should’ is used to say something that is the best to do or to say that someone ought to do something, and the person must do it. E.g. 

Riya could visit us on Saturday. (It is a possibility. Riya may or may not visit the speaker on Saturday.) Riya should visit us on Saturday.

(This is more like Riya has to visit them on Saturday, or she visiting on Saturday is a nice idea.)

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Could is the past tense of ‘can’, which is used to describe an ability. It is used when someone is referring to an ability in the past. It is a conditional verb that expresses ability or past possibility.

Eg. In high school, I could play volleyball. It is used as a modal verb to describe a possibility in the present and future tense.

Should is the simple past tense of shall. It is an auxiliary verb that has very few uses. It can also be used in case of questioning or for future events.

‘Should’ is used to say something or ask someone the correct way to do something or the right thing to do. Eg. Should I apologize to him for what happened yesterday? 

Comparison Table Between Could and Should

Parameters of ComparisonCouldShould
Meaning‘Could’ refers to possibilities in the past or to an event that has a probability of happening.  ‘Should’ refers to a person’s responsibilities, advises, suggestions and corresponds to the best outcome of any scenario.
Root verbCanShall
TensePast tense of canSimple past tense of shall
UsagePast conditional
Used in making requests, suggestions, asking questions, or seeking permissions.
In indirect speech
Used in giving suggestions, advice, and recommendations.
Nature of speechFormalInformal

What is Could?

‘Could’ is an auxiliary verb used to express a past possibility, i.e. something possible in the past. It can be used in various situations and circumstances.

Could is sometimes used in conditional sentences. If I had more time this weekend, I could visit my parents. The use of ‘could’ is also seen while describing the ability in the past. When I was younger, I could walk 1 km in 10 minutes.

Use of could for the possibilities in the future, in case of upcoming events. You could put up the banner on display for the festival; we could go to the beach together this weekend. 

Use of could is done to make a request or while asking something. Could you please pass me the menu?

Use of ‘could’ to point out something you can do or are allowed to do. She said that we could go to the movies after completing the assignment. 

Use of could is observed while giving a suggestion. We could order tea instead of coffee. It is also used to indicate politeness in your speech. Could you please come over to this counter for a while?

What is Should? 

‘Should’ is an auxiliary verb, past tense of shall, and used to deal with obligations, propriety, expediency, and deductions.

It is also used to express ideas and preferences or to give recommendations or advice to someone. E.g. You should focus more on your health and less on your work.

When we have to say that this is the right thing to do, we use should, i.e. You should do this. Use of should is observed while advising someone. 

You should visit a doctor and get your check-up done. Use of should is seen while explaining a probable event or an expecting moment. The pizza delivery should be here by 9.00 P.M.

Use of should in case of showing obligation. You should brush your teeth before going to bed. It is also used to express the conditionals. 

If I lost my job, I should have no money left with me. Use of ‘should’ to express futurity from the point of view from the past. I realized that she should have done most of the work beforehand.

Main Differences Between Could and Should

  1. Could express an idea, gives an option or a solution for someone else. Used to express strong opinions or strong advice.
  2. Could do not expresses any kind of judgment or final answers. It only talks about probability, about one of the two or more situations. Should speak about the most advisable and best outcome for a situation.
  3. While using ‘could,’ we let the third party be a decision-maker, while ‘should’ is used to solidly influence the decision-maker.
  4. Could is used for sharing ideas or views to senior or elderly, where we ought to use a formal speech, while the latter is used to express the ideas or decisions of the decision-maker or to express what is right to do.
  5. While ‘could’ is used for describing a possibility, ‘should’ is used for the right choice or decision.
Difference Between Could and Should


Both could and should have different usage, though sometimes it can be used in the same situations depending upon the voice of speech.

Could is used formally and shows a polite attitude towards the listener. Should is used to show the superior power of speech while advising or recommending, or making a decision.

Could and should are used to describe the probable events and the things which are right to do respectively.

While ‘could’ is used in informal speech with family and friends, one should always use should in a formal speech while addressing something and politely.

The usage of the word in your sentence describes the tone of your sentence.

‘Could’ is used as a modified form of ‘can’ and should is the modified form of ‘shall’, and both give the same impression as their root verb when used in a sentence.

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