Unit 36 Similarities, differences, and conditions
A Similarities
 
Joe is similar to / like his brother in many ways. Joe and his brother are very similar.
Joe and his brother are (very much) alike.
Sue and Pat both passed their exams. [Sue passed and Pat passed.] But neither (one) wants to go to college. [Sue doesn't want to go, and Pat doesn't want to go either.]
The two boys have a lot in common. [They have many things, e.g., hobbies, interests, beliefs, that are the same or very similar.]

B Differences
 
Paula is not at all like / (quite) unlike her sister Pam. [very different from]

They have nothing in common, [no interests, beliefs, etc., that are the same] His early movies are (quite) different from his later ones.

C Using compare
 
We want to compare the prices of all the cameras before deciding which one to buy.
They made a comparison of average salaries in different parts of the country.
Our new home is very big compared with/to our old one.
If you compare this one with the others, I'm sure you'll see a difference.

D Exceptions
 
When we make a general statement about things or people, and then say that one thing or person is not included or is different from the others, we use these words and phrases:

It snowed everywhere except on the west coast.
The two girls are very similar, except that Marie has slightly longer hair.
The museum is open every day except (for) / apart from Sunday(s).
Everyone heard the fire alarm except (for) / apart from the two boys in Room 7.

Note: Except can be followed by different words (nouns, prepositions, etc.), but except for and apart from are followed by nouns or noun phrases. Apart from is more formal.
E Conditions
 
Notice the tenses underlined in the examples.

We will be late unless we hurry. [We will be late if we don't hurry.]
Unless the weather improves [if the weather doesn't improve)], we won't be able to go.
I have to go now; otherwise I'll miss the last bus. [if I don't go now] You can borrow it as long as* you bring it back by Thursday, [on condition that] Take your umbrella in case it rains, [because it may rain later]

*Note: The meaning is very similar to if here, but the use of as long as shows that the condition is very important to the speaker.