1. That's fine with me.

(Does 'with' mean 'being related to'?)

4. It's raining hard.
5. It's raining heavily. 2. It's raining much.
3. It's raining a lot.
6. It's raining cats and dogs.
(Are they all the same in meaning? Can we use 'much' instead of 'a lot'?) •English - Steve, Saturday, November 12, 2016 at 5:53am
#1. I don't think that's a good explanation. It just means that I agree.

#2 nope - However, it's common to say "It's not raining much"
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Thank you for your help.

2. It's raining much.
3. It's raining a lot.
2-2. It's not raining much.

Do you mean #2 is not used? Why is that?
#2-2 is used commonly, right?

I'm not sure why #2 is not used. It just isn't!

#3 is used a great deal, however, and so is #2-2.

1. Yes, in the phrase "That's fine with me," the word "with" does imply being related to or in agreement with something. It suggests that the subject finds no issue or objection with the situation or statement being discussed.

2. In terms of the different expressions about rain, they all convey a similar meaning of rainfall being heavy or intense. However, there are some nuances that differentiate them:

- "It's raining hard" emphasizes the intensity of the rain, suggesting that it is coming down forcefully.
- "It's raining heavily" also signifies a strong rainfall, but it may imply a greater amount of water being released from the clouds.
- "It's raining much" is not commonly used in English to describe heavy rain. While it is grammatically correct, it sounds less natural to native speakers.
- "It's raining a lot" is a more common and casual way to express heavy rainfall. It indicates a significant amount of rain.
- "It's raining cats and dogs" is an idiomatic expression used to describe a very heavy rainstorm. It is often used figuratively and emphasizes the sudden and intense nature of the downpour.

Regarding your second question, you are correct. Saying "It's not raining much" is indeed a common expression when the amount of rainfall is relatively small or insufficient. However, the simple statement "It's raining much" without the negation is not commonly used in English. This is likely because native speakers tend to use other expressions, such as "It's raining a lot," to convey the same meaning.

It seems there was an error in the numbering of your questions, but I hope this explanation clarifies the usage of these phrases when talking about rain.