A parable is a story that can say almost anything but the bottom line must be true. Miriam Webster's Collegiate Dictionary defines "parable" as: "A usually short fictitious story that illustrates a moral attitude or religious principle."
An allegory must be true in all points. Webster's 1828 dictionary gave the definition of allegory as: ". . .a figurative description of real facts. An example is given as Psalm eight where God's chosen people are represented as a vineyard.
A lot of ministers try to say that the story of the rich man and Lazarus
was not a parable, but it has all the ear-marks of a parable. When it says
a certain man, the word "certain" is from the Greek word "tis" which means
"some" or "any," not very specific as we think of certain. I believe this
story to be a parable and that the bottom line is all that is being taught.