'I Couldn't Undertand' Vs 'I Didn't Understand'?

I have thought about this question, and quite honestly I don't think think there is any appreciable difference between the two.

There might be a very slight difference, as follows:

1. I couldn't understand a word he said. (this might suggest that he spoke unclearly or his words weren't audible)

2. I didn't understand a word he said. (might suggest that you heard what he said but didn't understand his meaning)

Basically, "couldn't understand a word he said" and "didn't understand a word he said" both mean the same thing.

Perhaps someone else can give a better answer to this question.

I'd agree.

'I couldn't understand...' — used where someone has a strong accent, or mumbles.

'I didn't understand...' — used where the meanings of the words are unintelligible, e.g. in a Human Resources presentation.

But as taiwandave says, you could use either in either situation.

MrP

"can" (or "could") are used in English with no added meaning before verbs of perception, "remember", "understand", and possibly a few others. Many other languages do not use their word for "can" in these contexts unless it literally refers to some ability (as in the last two examples below).

I can see it from here. (more idiomatic)
I see it from here. (also grammatically correct)

I could smell something burning. (more idiomatic)
I smelled something burning. (also grammatically correct)

I can't remember what he said. (either is fine)
I don't remember what he said.

Could you understand his diagram? (either is fine)
Did you understand his diagram?

But note: I'm getting old, so I can't remember things very well anymore. ("don't remember" possible, but a little less appropriate)
And: He has the eyes of an eagle. He can read very fine print. ("reads" possible, but considerably less appropriate, in my opinion)

i understood it , but i have one querry abt could , as i know could use for past , but some time why it is using for present like example ;- in childhood i couldnt speak in english but now i can .
could you plez pass it , could you plez speak loud

This thread is almost 10 years old. It is better to start a new thread in these cases.

Anonymoususing for present like example ;- in childhood i couldnt speak in english but now i can

This is not using 'could' as a present tense.

Anonymouscould you plez pass it , could you plez speak loud

You have several errors.

Could you please pass it? Could you please speak louder?

In these cases a past tense form is used to make a polite request. This is a typical use of the past.

CJ

Hello, could you please helo me with this one?

"I couldn't understand what you meant/mean..."

In which form should i use the second verb if i'm talking about the past?

Anonymousif i'm talking about the past?

Use the past form: meant

CJ

Here in the above, could not can be used when you actually tried to understand but you could not understand his sayings and it could be because of his/her accent or any other reason but it clearly conveying that you tried and was not able to understand an

But in case of using i did not understand , it just conveys that you did not understand him and the reason could be your inability to understand. hope this makes sense i cannot explain any better than this