"One of the most basic and powerful of human cognitive processes is the ability to comprehend and express that two things are similar or different". (Celce-Murcia and Larsen-Freeman, 2009)
Take a look at this:
"You should be stronger than me
You've been here seven years longer than me"
These are two lines from a song entitled "Stronger than me", performed by Amy Winehouse. In this part we are comparing two elements - you x me.
In English, it works like that:
For short adjectives, up to around six letters (sorry for not being precise but, yes, it's around six letters, for this is no mathematics), we just add the end er to the word.
So, I say:
Paulo is stronger than me.
Today is colder than yesterday.
For longer adjectives we don't add er. We add a new word before the adjective: more.
So, I say:
Now, try to compare the following elements, using the adjectives given (check the answers):
1- a house x a car - expensive
2- a house x a car - cheap
3- my best friend x I - tall
4- my best friend x I - short
5- Portuguese x English - easy
6- Portuguese x English - difficult