Question
Ok, this will an easy one for you!  My friends and I got into a debate on what are annuals and what are perennials.  What is the definition of perennials?

Answer
I must say,this is THE easiest question I have answerd yet!
Thank you for that!
OK here goes:
A perennial means that the plant OR the offspring of the plant(also could be dropping seed or root multiplication from same plant)will return year after year without fail.

An annual plant means just that.Annual means yearly.The plant will be produced ,bloom(or not)and die in the same year. These are annual bedding plants like Petunias,Marigolds,Impatiens,Lantana,Wax Begonias,Alyssum,Ageratum,Geraniums,etc. But sometimes if a annual is in a protected spot like near the houses heating unit or a warm spot that is protected from winter winds they can pop back up the next year.Maybe not as robust,but there are usually some survivors that can surprise you.

However,here is where it gets tricky.Let me point out that some of those annuals are also considered perennials in warm climates. That's why we classify planting zones all over the US. The zones are 1 through 11. 1 being the coldest like the extreme uppermost northern states and up into Canada and 11 being the warmest like the tip of Florida,Texas and coastal California.They can grow just about anything all year around with the EXCEPTION of spring blooming bulbs that HAVE to have a dormant 3 to 4 month cold period which zones 8 to 11 cannot provide.

And to make things even more confusing there are the biennials that take a while to produce a plant.The original parent plant will drop seed and that plant will put on leaves but will not bloom until the next year.Therefore it takes 2 years to produce a biennial.

Hope this is helpful to you. The classification of plants on the whole seems very black and white,but with plants, as in life there are always shades of gray.