Connecting ideas

1- Connecting ideas with AND:
When and connects only two items within a sentence, no 
comma is used. When and connects three or more items 
in a series in a sentence, comma is used.
They saw a cat and a mouse.

He saw a cat, a mouse, a man, and a woman. 
(and connects nouns)

I opened the door, walked into the room, and sat down at my desk 
(and connect verbs)

Their flag is red, yellow, and black. 
(And connects adjectives)

The comma before and is optional.
When and connects two sentences a comma is usually used.
I saw a bird, and she saw a sun.

Two completes sentences (also called independent 
clauses) are separated by a period, not a comma.
 I saw a bird. She saw a sun.
A period = full stop (British English)

 
2- Connecting ideas with BUT and OR:
I went to bed but couldn’t sleep.
Is this a book or an exercise book?
Did you order coffee, tea, or milk?

And, but and or are called  “conjunctions”. But and or 
are used in the same ways as and.

I dropped the vase, but it didn’t break.
I dropped the vase. But it didn’t break. (Also possible)
Do we have class on Monday, or is Monday holiday?


3- Connecting ideas with SO:
I frequently use the e-mail, so I rarely write letters. We 
aren’t in the paper age anymore.

So can be used as a junction. It is preceded by a comma. 
It connects the ideas in two independent clauses.  So expresses 
results:
Cause:      I frequently use the e-mail: 
Result:   I rarely write letters.


4-  Using auxiliary verbs after but and and
He doesn’t like coffee, but his wife does.
She likes tea, but he doesn’t.            
He isn’t here, but she is.
She won’t be here, but her husband will.
They have learned Spanish, but she hasn’t.
He likes Mathematics, and she does too.
I don’t like some music, and she doesn’t either.
I won’t go downtown, and he won’t either.
They didn't pass the exam, but she did.
 

After but and and often a main verb is not repeated. 
Instead, only an auxiliary verb is used. This auxiliary 
is a substitute for the main verb phrase. 

The auxiliary after but and and has the same 
tense or modal as the main verb. 
Keep in mind that we have not contraction of a verb 
with a pronoun at the end of the sentence. 

He isn’t here, but she is. Not but she’s.
Notice that:
	- With BUT, we use the opposite.
	- With AND, we don’t use the opposite: TOO with 
affirmative sentence. EITHER with negative sentence.

 
5-  Using AND + TOO, SO, EITHER, NEITHER:
She likes milk, and he does too.        
She likes milk, and so does he.
She doesn’t like milk, and he doesn’t either.
 She doesn’t like milk, and neither does he.
Do you like Math? So do I.

Too:   With so
Either:With neither

Keep in mind that with neither we have an 
affirmative auxiliary

With two speakers:
  -    I’m hungry.
I’m too.  So am I. (Me too: is informal)

I don’t hear from you!
-         I don’t either. Neither do I. (Me neither is informal)

Remark that with two speakers, and is usually not used.

 
6- Connecting ideas with BECAUSE:
He called his friend  because he needed her.
Main clause             adverb clause

Because he needed her, he called her.

Because expresses a cause. It gives a reason. It 
introduces an adverb clause.

A main clause is a complete sentence.
An adverb clause is not a complete sentence.

 
7- Connecting ideas with even though/although: 
Even though (although) I was thirsty, I didn’t drink.
I didn’t drink even though (although) I was thirsty.

Even though and although introduce an adverb clause.

Even though (although) I was thirsty, I didn’t drink.
Because I was thirsty, I drink.

Because expresses an expected result. Even 
though / although expresses an unexpected or opposite 
result.