# What C is to D, (so) A is to B. As C is to D, (so) A is to B.

#### younghon

##### Senior Member
A is to B as C is to D= A is to B what C is to D = What C is to D, (so) A is to B. = Just as C is to D, so is A to B. =As C is to D, (so) A is to B.

**A Do for B What C do for D.

Q:Hi! I'm a man who learn English in Korea. I have some questions.

1. What C is to D, (so) A is to B.
Can we put so in above sentence?

2. As C is to D, (so) A is to B.
Can we put so in above sentence?

3. A Do for B What C do for D.
<-----Out-of-scope question removed by moderator (Florentia52)----->

Thanks in advance!

Last edited by a moderator:
• #### Chez

##### Senior Member
Your sentences 1 and 2 are better with 'so' in them.

I think your sentence 3 is only possible with the verb in the singular:
A does for B what C does for D.

Studying does for your brain what running does for your body (i.e. exercises it)

#### younghon

##### Senior Member
I appreciate it.

#### Forero

##### Senior Member
1. What C is to D, (so) A is to B.
Can we put so in above sentence?
I wouldn't. "What C is to D" does not mean the same as "As C is to D".
2. As C is to D, (so) A is to B.
Can we put so in above sentence?
Yes, and with so, you can invert:

2'. As C is to D, so is A to B.

"So" here means "as C is to D", so it is redundant, but it provides emphasis (like "just as" instead of plain "as") and is acceptable.
3. A do for B what C do for D.
This is fine too, assuming "A" and "C" represent something plural.

#### younghon

##### Senior Member
Thank you very much for your detailed explanation!

#### Englishmypassion

##### Senior Member
2'. As C is to D, so is A to B.

"So" here means "as C is to D", so it is redundant, but it provides emphasis (like "just as" instead of plain "as") and is acceptable.

Do you mean As C is to D is A to B is the original, natural, construction?

(I wouldn't use so in 1 either.)

Thanks.

#### Uncle Jack

##### Senior Member
I agree with Chez on including "so" in (1) and (2) and I am a little puzzled by Forero's suggestion of inverting the second clause in (2), so I wonder if "as...so..." is used differently in American English. I think it works far better using exactly the same structure for both clauses.

A and C need to be plural in (3), or you can change "do" to "does" and use singular terms. You can also have plural in one clause and singular in the other.

#### Englishmypassion

##### Senior Member
(2) and I am a little puzzled by Forero's suggestion of inverting the second clause in (2), so I wonder if "as...so..." is used differently in American English. I think it works far better using exactly the same structure for both clauses.

Surprising! I find the inversion perfectly natural and that's how I would write that.

#### younghon

##### Senior Member
I think Uncle Jack's opinion is right that it is better to use exactly the same structure for both clauses and I understand that 'so is A to B' is inversion.
Am I right? I undestand' so is A to B' is an inversion.

#### younghon

##### Senior Member
You posted at the same time with me.
Anyway Thanks a lot! Englishmypassion.

#### Forero

##### Senior Member
Do you mean As C is to D is A to B is the original, natural, construction?
No. I mean that "so" means "in that (very) way", which in context means "(just) as C is to D". "So" is adverbial and allows inversion. "As C is to D" also allows inversion, but not as readily as "so".
I think Uncle Jack's opinion is right that it is better to use exactly the same structure for both clauses and I understand that 'so is A to B' is inversion.
Am I right? I undestand' so is A to B' is an inversion.
The natural order is "A is to B as C is to D." Putting "As C is to D" first changes the emphasis, adding "so" adds stress, and inverting after "so" enforces the intended meaning of "so".

Which structure is "better" depends on the intent of the writer.