leopard gecko help

Question
QUESTION: Can i put another gecko in with a leopard gecko that hasn't seen a another gecko in years??

ANSWER: Hi Max,
That depends...
If you are meaning another species of gecko...I don't recommend it at all.. remember, in the wild species don't intermix... so its best to keep it that way in captivity also.
If you are referring introducing another leopard gecko:

if your leo is a male and you want to place a male with it..no..males can never be housed together.

Males and females should only be placed together for a short time for breeding purposes.

Females generally get along, if given enough space.  I would not attempt it in less than a 30-40 gallon tank or larger.
If both are the basically the same age and size, it may be OK...I would place them in a neutral cage...meaning one that neither has been in..that way there are no territory issues.  Be sure to watch for any problems.  Any new leo brought in to your home also needs to be quarantined for at least 30 days before allowing them together.
Remember...never two males..
male and female...only for a short time for breeding purposes..
female and female...MAY work out if given enough room and introduced in a neutral cage..both basically same age/size.

---------- FOLLOW-UP ----------

QUESTION: i ment if i were to introduce a 5-6 month old leopard gecko with a 4yr old gecko that hasnt seen a gecko in years what would they do? would they fight or would the older one eat the younger one?

Answer
Max,
As I said in my previous answer, it depends on the sex and the size of them, and a lot more...  It also depends on the personality of both geckos. It depends on the size of the tank...
there is no way to know if they will get along...they may fight...they may get along (there than two males) the older may bully the younger one and the younger one will stress.  
If you keep them in separate tanks which they can see each other and see their reactions, that will give you a better idea.
All reptiles are different....some are accepting, some do not want any company ever...Will the older attack the younger one?  No one really knows...the younger may even attack the older one.
If you want to house two leos together, introduce them properly and wait til the younger one is a bit older, but keep a close eye on how they react to each other through the glass of two tanks, and then in a neutral area...where they can interact.
They are basically wild animals, no one can really know what they will do, other than two males which will fight.