Interesting topic. It's my belief, that a ghost would s[eal on whatever language they spoke when they were alive.
I agree with Bkiff, because why would they know any other language then what they died with. Unless... all spirits are somehow connected with universal knowledge.
To me it seems is based on there native tongue, maybe even some are bi or tri lingual. Then theres angels they use for writing a form called "Angelic Script" its an old form from long ago i was first shown it in my teen yrs in dreams when my parents house's activity started to get worse. I was using it along side with chalk for my door frame and floor for protection at night. They always attack the sensitives.
i was having alot of obe's i guess i dont like to call it astral travel but out of body experiances anyway .i thought i was going crazy and didnt know where to turn other than a shrink and i didn't realize it for what it was till i read comunnion by whitley streiber and he mentioned robert monroe and a book called journeys out of the body and then read far journeys he actually has a institute and examined it in a scientific way and was successful in producing out of body experiances in people who have never had one ill put a link to his site after.
anywas about spirit language and how he comunicated was in picture form or thought form like if i could read your mind and vice versa rather than words i would say get out of house by thinking of you walking out of house or if you were a hidden i would think of you walking up to me ..Etc
i would say spirits feel our thoughts more than they listen to our words but thats just my guess and have never really tried comunication but have felt it and it is has always been as i said in the form of actions or thoughts...so maybe less talk and more action lol is best for spirit comunication ..im no expert but just shareing whats happened to me and what i read...
here is the link to the monroe institute
http://hemisyncforyou.com/monroeinstitute/
Speaking of ghost language, in one of your recent investigations, a viewer sent a text to the team about how to say something in "Native American". Do you know that there were over one thousand Native American languages with over 800 surviving today? They were all very different from each other. To say that all Native Americans said hello the same way would be like saying that all Europeans say hello the same way. Just FYI.
Also when investigating a location with a Native American haunt - here is a tip from me, a Chinook Indian - do a little research on what tribe was there and find out how they said, "Hello friend." Historically speaking with many tribes, if an outsider showed enough respect by speaking those two words in their tribal language, they would welcome that person into the tribe as a friend. You might find some interesting results with that.