Confusion in using these two words has and have

[Dorjee]

I often make mistakes in using these two words has and have, can and could.

Please help!

[Yankee]

Hi dorjee

I see that you have been posting TOEFL essays, so I assume you have noticed problems with has/have and can/could in your essays.

Why don't you post some specific sentences for further discussion? These should be sentences in which you made an error or sentences you are unsure about. Without more specific input from you, your question cannot be effectively answered.

Until then, I'll start with a few very general rules for has vs have:

You need have when the subject is: I, you, we or they

You need have when the subject consists of two singular words connected by the word 'and' (for example, John and Mary)

You need has when the subject is he, she or it
(in other words, when the subject is third person singular)
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Amy
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ESL teacher, and native speaker of American English

[Dorjee]

Thank you so much, it become little clear. However, there is still some confusion, like what is different between;

Can I talk to Mr. John? or
Could I speak to Mr. John?

Likewise;
She has gone to market.
Have you gone to market?

[Yankee]

Hi dorjee

There are a variety of ways that can and could are used. In your examples, whether you use can or could is a question of politeness or formality. I understand both sentences as requests to speak to Mr. John.

Can I talk to Mr. John? Using 'can' is more informal or casual.
Could I speak to Mr. John? Using 'could' is more polite (and more formal).

For you second pair of sentences, look at my previous post. Your sentences use the present perfect tense and the "rule" I gave you in my first post applies.

She has gone to market. (Subject = she, verb = has gone)

Have you gone to market? (Subject = you, verb = have gone)

Amy
_________________
Amy
.
ESL teacher, and native speaker of American English