What is the meaning of these words/sentences?


I've some issues getting through the message of my language correspondence
partner:

> 日本では、たくさんの花火大会があります。
>
> ７月には、神戸の花火大会、大阪の花火大会に **多くに** 人が訪れます。
>
> **１万発** _で_ とても迫力がありますよ。
>
> あと、 **夏になるとセミがたくさん鳴いて** 、外はとてもうるさいです。

Content-wise, I understand what I'm being told here, but I don't understand
how some things work and therefore also have problems determining what exactly
is being said.

> 1) 多くに

Why is there a に attached? I think that 多い shall become an adverb here, but い
adjectives become adverbs solely by replacing い with く.

I could imagine 多くに in context of a sentence like this:

[code]

    人は多くになりました。
    
    It became a lot of people/The people got numerous.
    
[/code]

But first I don't know whether this assumption is correct and second I don't
see whether なる and 訪れる could be treated equally concerning this case.

> 2) １万発

What does this 発 mean? 万 is まん but the other one I couldn't find a satisfying
entry on jisho.org, especially not in connection to 発.

> 3) Since I don’t really know 万発 I have trouble interpreting the meaning and
> function of this で
>
> 4) **夏になるとセミがたくさん鳴いて**

I don’t really know about this one. It's something about `“when it becomes
summer”` and… `“the half”`???

I think it's about some half which sings loud, but I have trouble integrating
the conditional clause meaningfully into the full sentence.




> 1) 多くに in 大阪の花火大会に多く **に** 人が訪れます。

It is typo. It should be 多く **の** , so 大阪の花火大会に多くの人が訪れます means _A lot of
people visit Osaka to see the festival of shooting off fireworks_.

> 2) １万 _発_

発 is a counter to count fireworks. It is also used to count bullets or
cannonballs. １万発の花火 is 10,000 fireworks.

> 3) since I don’t really know 万発 I have trouble interpreting the meaning and
> function of this で

１万発で implies **１万発** の花火が上がるの **で** _since there are 10,000 (shooting off)
fireworks_.

> 4) 夏になるとセミがたくさん鳴いて I don’t

セミ is a cicada, that is written as 蝉 in _kanji_.

* * *

# EDIT:

As for the meaning or function of で in １万発 **で** とても迫力がありますよ, naruto gave me a
comment to my answer as "this で after 1万発 is the te-form of the copula だ", so
I'll consider it further.

I quote the explanation of the te-form of the copula だ from
[here](http://people.uncw.edu/kanoy/practices/desu_te.htm).

> ### **Te-form of copula (-です)**
>
> This form let adjectives connect to other adjectives or verbs.  
>  **"です" changes into "で" + another sentence.**  
>  In the past, we used these choppy sentences: 名前は、一郎です。 年は１８才です。
> せんこうはアメリカ文学ぶんがくです。  
>  If we use te-form of desu, these sentences can be connected smoothly as
> follows:  
>  名前は、一郎 **で** 、年は１８才 **で** 、 せんこうはアメリカ文学（ぶんがく）です。 (lit. My name is Ichiro,
> age is 18 years old, **and** major is American Literature.)

Reading this explanation, "te-form of copula" shows that it has a function to
connect plural sentences having the same subject simply by "and" into one
sentence. Applying this rule to OP's sentence "１万発 で とても迫力がありますよ。", you could
understand that there were two sentences at the beginning as "１万発です。" and
"とても迫力がありますよ。" Because their subjects were omitted, by complementing the
subject you'll get two senteces like " **花火は** １万発です。 _The fireworks are
10,000 shots_ " and " **花火は** とても迫力がありますよ。 _Fireworks are very powerful and
impressive_."; or " **打ち上げられる花火は** １万発です。 _Fireworks launched are 10,000
shots_ " and " **打ち上げられる花火は** とても迫力がありますよ。 _Fireworks launched are very
powerful and impressive_."

Here we can confirm that the rule of "the te-form of the copula だ" functons.
Although this rule fuctions, it certainly seems that the combined sentence is
monotonous because we merely joined the two sentences with "and".

So I interpreted the で in "１万発 **で** とても迫力があります" as the short form of **なので**
that means a conjunction as " _because_ or _since_ " in the original answer.

With this interpretation, the two sentences become a causal relationship that
makes the combined sentence lively, which the writer of the letter might have
thought apart from whether the writer knew the grammatical rule or not.




> 1) 多くに in 大阪の花火大会に多く **に** 人が訪れます。

It is typo. It should be 多く **の** , so 大阪の花火大会に多くの人が訪れます means _A lot of
people visit Osaka to see the festival of shooting off fireworks_.

> 2) １万 _発_

発 is a counter to count fireworks. It is also used to count bullets or
cannonballs. １万発の花火 is 10,000 fireworks.

> 3) since I don’t really know 万発 I have trouble interpreting the meaning and
> function of this で

１万発で implies **１万発** の花火が上がるの **で** _since there are 10,000 (shooting off)
fireworks_.

> 4) 夏になるとセミがたくさん鳴いて I don’t

セミ is a cicada, that is written as 蝉 in _kanji_.

* * *

# EDIT:

As for the meaning or function of で in １万発 **で** とても迫力がありますよ, naruto gave me a
comment to my answer as "this で after 1万発 is the te-form of the copula だ", so
I'll consider it further.

I quote the explanation of the te-form of the copula だ from
[here](http://people.uncw.edu/kanoy/practices/desu_te.htm).

> ### **Te-form of copula (-です)**
>
> This form let adjectives connect to other adjectives or verbs.  
>  **"です" changes into "で" + another sentence.**  
>  In the past, we used these choppy sentences: 名前は、一郎です。 年は１８才です。
> せんこうはアメリカ文学ぶんがくです。  
>  If we use te-form of desu, these sentences can be connected smoothly as
> follows:  
>  名前は、一郎 **で** 、年は１８才 **で** 、 せんこうはアメリカ文学（ぶんがく）です。 (lit. My name is Ichiro,
> age is 18 years old, **and** major is American Literature.)

Reading this explanation, "te-form of copula" shows that it has a function to
connect plural sentences having the same subject simply by "and" into one
sentence. Applying this rule to OP's sentence "１万発 で とても迫力がありますよ。", you could
understand that there were two sentences at the beginning as "１万発です。" and
"とても迫力がありますよ。" Because their subjects were omitted, by complementing the
subject you'll get two senteces like " **花火は** １万発です。 _The fireworks are
10,000 shots_ " and " **花火は** とても迫力がありますよ。 _Fireworks are very powerful and
impressive_."; or " **打ち上げられる花火は** １万発です。 _Fireworks launched are 10,000
shots_ " and " **打ち上げられる花火は** とても迫力がありますよ。 _Fireworks launched are very
powerful and impressive_."

Here we can confirm that the rule of "the te-form of the copula だ" functons.
Although this rule fuctions, it certainly seems that the combined sentence is
monotonous because we merely joined the two sentences with "and".

So I interpreted the で in "１万発 **で** とても迫力があります" as the short form of **なので**
that means a conjunction as " _because_ or _since_ " in the original answer.

With this interpretation, the two sentences become a causal relationship that
makes the combined sentence lively, which the writer of the letter might have
thought apart from whether the writer knew the grammatical rule or not.

