Could vs Should: Difference and Comparison

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 experts figure out the difference, but it seems similar to people when used daily.

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

Key Takeaways

1. “Could” refers to the ability to do something, while “should” implies a moral obligation or duty to do something.
2. “Could” indicates a possibility, while “should” indicates a recommendation or advice.
3. “Could” can express hypothetical or future events, while “should” often indicates a present or past event.

Could vs Should 

“Could” is used to express possibility or ability. It can also be used to make a request or offer. For example: “I could run faster when I was younger” or “Could you please pass the salt?” “Should” is used to express advice or a recommendation. It can also be used to express a duty or obligation. For example: “You should exercise every day” or “I should have finished my work by now.”

Could is the past tense of ‘can’, which describes 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 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

Parameters of Comparison	Could	Should
Meaning	‘Could’ refers to possibilities in the past or an event that is probable.	‘Should’ refers to a person’s responsibilities, advises, and suggestions and corresponds to the best outcome of any scenario.
Root verb	Can	Shall
Tense	Past tense of can	Simple past tense of shall
Usage	Past conditional Used in making requests, suggestions, asking questions, or seeking permissions.	In indirect speech Used in giving suggestions, advice, and recommendations.
Nature of speech	Formal	Informal

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 allow 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. 

The could is used to make a request or while asking something. Could you please pass me the menu?

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

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

You should visit a doctor and get your check-up done. The use of should is seen while explaining a probable event or an everyday 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 would have no money left. Use of ‘should’ to express futurity from the point of view of 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 not express any judgment or final answers. It only talks about probability, about one of 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 influence the decision-maker solidly.
4. Could is used for sharing ideas or views with seniors or the 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’ describes a possibility, ‘should’ is used for the right choice or decision.