Big and Large

  What's the difference between  big and large ?  Both they are adjective. 
I reference much information but I still can't figure out it.
It is very difficult to definition they.  We usually use a phrase " a  large amount of  " and
" a large number of " and then plus number. I think it' depend on you describe somethings.
We need reading much article and you will get rules. Soomeday you make a sentence
which is the best choice by natural. 

I like useing Cambridge Advanced Learner's Dictionary.
 It's very clear and guickly.

6.4-magnitude quake hits southern Taiwan

epicenter
definition: the part of earth surface directly above the origin of earthquke
The 921 epicenter was happened at  Nantou.

rumble
definition: a rumbling sound
A rumble of thunder.

juncture
definition: a state of affairs or point in time
At this juncture in our nation's  affairs ,  we need find leadship.

alter
definition: change : make different
He has altered since his illness. 

announce
definition: make known publicly
He announces the six o'clock news.

Hello everybody

   Welcome to visit my blogger. My name is Honda. I come from Yunlin county. Dapi is my hometown. Dapi is famous for pickled cabbage. I can speak three language. They are Taiwanese,Mandarin and English. English is my second language. I like to momery vocabulary,but I can`t speak fluently. I want to improve my listening and pronunciation.
  I  major in Chemical Engineering. There are a lot of tests  in department of Chemical Engineering (Che.) . For example: quiz, review test , final exam and homework . My doctor is strictly to student. Be carefully ,
I will fail you.
What's difference between dept of Chemistry and dept of  Chemical Engineering . Chemistry is emphasis on theory,and do experiment in Laboratory.Chemical Engineering  is good at mass produce (Chemical processes) and how to save money.  We  study a varity of domain. For example:Biochemical,enviroment,Polymer, Nanopartical material,Solar cell and Petrochemical. After graduated from school,we can enter different company. Thanks for your reading.