Question - Define Regular Expression?
Answer -
Regular Expression is the generalized form of any regular language through which you can construct any string related to that language.
Take an example from your handouts
L1 = {Λ, a, aa, aaa, …} and L2 = {a, aa, aaa, aaaa, …} can simply be expressed by a* and a+, respectively.
so a* and a+ are the generalized form of Languages L1, L2.
And a* and a+ are called the regular expressions (RE) for L1 and L2 respectively.