I just realize i always misinterpret the meaning of learning curve. So here are the definitions on the internet.

From Wikipedia

The expression steep learning curve is used with opposite meanings. The term is often used in common English with the meaning of a difficult initial learning process. Nevertheless, the Oxford English Dictionary, The American Heritage Dictionary of the English Language, and Merriam-Webster’s Collegiate Dictionary define a learning curve as the rate at which skill is acquired, so a steep increase would mean a quick increment of skill.

From StackOverflow

The term learning curve refers to the graphical relation between the amount of learning and the time it takes to learn.

From dictionary.com

A graphic representation of progress in learning measured against the time required to achieve mastery.

Here is a graphical illustration i got from StackOverflow.

proficiency
  |   __
  |  |
  |  |    Proficient in little time (steep = easy)
  |  |
  |_/____________
       time

proficiency
  |
  |       Proficient in lots of time (gentle = hard)
  |            __             
  |           /
  |__________/___
       time

And a picture~~

 

Done =)

Reference:

• StackOverflow – What’s a learning curve and why is steep not hard?
• Wikipedia – Learning curve
• dictionary.com – learning curve
• wordnik – learning curve