Can anyone explain the use of "has/have had"?

When it is prefered to be used?
It is noticed that if the second "had" is removed, there is no change in the meaning of sentence. Please clarify.

"have" and "has" are present tense:

"have had" is a combination of two verbs: present tense "have" and its past perfect object "had" + _____, like

I have had dinner. (I have eaten dinner)
I have had a bath. (I have taken a bath)

"had had" is a combination of two verbs: past tense "had" and its object,

If I had had a hammer . . . . (past conditional)
If I had a hammer . . . . (present conditional)

She has had a cold for two weeks now. / She's had a cold.
They have had a cold for two weeks now. / They've had a cold.

"has had" is for third person singular subjects (she, he, it), and "have had" is for the other persons and numbers (I, you, they).

"Have had" has nothing to do with the action itself, but the time you are talking about.

For instance

I drove a car - the action has finished and the time has also finished..
I have driven a car - this action has also finished, but the time is from a time in the past to NOW and not specifically the time of the action itself.

Likewise, I "have had" a lot of luck ... the being "having luck" does not continue into the present. The luck may have ended many moons ago.

The verb tense is called Present Perfect and it refers to unfinished time or unknown time of an event. It indicates that the action began at some point in the past and has not yet reached its end, or it is not important to know exactly when the action took place.

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The Me you have always known, the Me that's a stranger still.

Hello Last Island,

Can you please explain a bit more the use of "HAD HAD?" Also I have a sentence if you may put a detailed analysis of it. All the faith he had had had had no effect on the outcome of his life.

Regards,
RAO

Note: Sorry for replying the post, which is solely meant for somebody else.

Let me try to explain it a bit!

All the faith he had had had had

The combination "had had" in magenta colour - the latter combination - is referring to the time in the past finished before some past event.

Meaning past perfect tense was mandatory. In addition to that, note that it is also the "main verb" of the sentence.

Now let us talk about the former combination "had had" in orange colour.

It is kind of a relative clause(contracted version). I do not want to go more into the details and the rules of how to contract the relative clause, for it will confuse you a bit. All that pair(in orange) is saying that something happened before the past of the past.

In a nutshell, past (1) <- past (2) <- past <- present.

All the faith he had had(past of the past perfect tense + possession) (1) had had(past perfect tense + possession)(2) no effect on the outcome of his life.

I hope it helps you a bit to understand the concept.

Reminiscence: I used to play tense-game back in school days with my other friends. Therefore, I thought I should share my views as well.

P.S: Although that "had had had had" usage is grammatically correct, it sounds and seems obnoxious. Try to avoid using such construction as above in academic writing!

P.P.S: Sorry again for butting in and typing about the post which was not meant for me.

Regards.

Hello Islamabadkid,
You need not to be apologetic again and again. It was not mandatory for the addressed person to respond. It's a forum and anybody can put one's feedback.

Thank you.

RAO

The second had is used for possession.