Despite their ages I've had none of my current crew longer than 2 years. Billy (he's 6-7 but has been here 2 years) has developed an astounding vocabulary. He's not where Foxy or Muffin were but he's learning by leaps and bounds.
Luna's learning -- she's been here just over a year, and she was WAY better at communicating with dogs than other humans -- this has been a whole new idea for her to be 'social' with humans. She's always been good and sweet but the "wow - you're talkin TO me" thing was a new thing for her. But she too is developing an extensive vocabulary.
Kee's a foster -- she's older (somewhere between 10 - 16) and has never EVER been talked 'to'. It took her 3 months to truly "get it" when we gave her very elementary commands and expected her to "listen". This has been tough for her because she's not trusting -- humans have let her down sorely in the past so "don't get attached -- they'll dump you" is her motto.
But yeah -- they understand language and 'words'. Words become just like commands to them. I talk to them JUST like I'd talk to people. "Excuuuuuuuuuuse ME???? *I* don't think so!!!" (they're devastated!!!)
Just now, in fact, they've moved part of the fence of my back yard up about 12 feet so my back yard is 12' wider at one point. Luna went out and discovered immediately she could run LAPS!!!!
I said "Hoooooooooooooooooooooo HOOOOOOOOOOOOOOOOOOOOOO Run LAPS, Luna!!" and she did it again! A new 'word' was born -- and trust me -- she's gonna remember "laps" and when I tell her to go run some LAPS she's gonna know that means work off some energy and run in circles around the yard. It was a perfect place to teach her a new 'word'.
Billy, on the other paw, looked up at me and said "you don't mean ME do ya?" and I said "nope -- that's a Luna thing -- SHE can run laps! YOU stay with Mommy!" and he sat and did exactly that.
When he was in the hospital up at Gainesville I printed off his "posts" and "emails" every day and faxed them up there and his student actually READ them to him. Did he understand every word? nope. But he KNEW "email" -- he knows people talk to each other on the puter that way and that it was FROM MOM and BUDDIES. Eric marveled every day at the names Billy would recognize and how excited he got when Eric came to read to him. Yep -- he READ to a dog. and Eric said he quickly got over any feelings of feeling dumb simply because Billy loved it so much and understood it was 'news from home'. It motivated him in a big way and kept him from being depressed no matter how long he was up there (which was a week at a stretch a couple of times).
My dogs ALL understand "beddytimes away" (meaning a night spent away somewhere) and trust me -- they TOTALLY understand the difference between "Mom, Dad, Billy, Luna and Kee are all going beddytimes away" -- BIG HUGE excitement and they are esctatic all the while I'm doing preparations.
However -- in 10 days I"m gonna be planning a different beddytimes away -- David and I are going to visit my folks up North. Luna and Kee are going to Miss Emily's Bed and Biscuit (Luna's second home - she did doggie daycare there constantly before David and I took her), and Billy's going to stay with my vet at his home (cos he can't go where he might encounter sick dogs because of the whole IMHA thing).
Whole different kind of excitment -- because we're all going in different directions and they WILL understand that (because they know "Miss Emily's" and "Dr. Bailey's" and know they are different places). They'll all have a good time, but it's NOT the 'fun time' that it would be if we were all going together. "Beddytimes away" has a very very specific meaning for them and they understand if it's a family time or NOT.
They also have a rudimentary idea of numbers and the passage of time. When I get stuff ready for them to go to Miss Emily's and Dr. B's I will package their food for each day. And they KNOW when they run out of packages MOM WILL BE HOME. I will also pair that with a number of fingers because I want them to understand it's a finite time -- not that they are being abandoned.
I mate words with "time" -- "going to work" means I"m gonna be gone all day long and I'll be home before supper. They know Firecracker Day. They know "Christmas Tree day". Valentines, Easter -- these mark time for them.
My point is - your pup will know whatever words you TEACH them. Mine understand the difference between Dad's home, and when he PHONES. (cos just because he phones doesn't mean he's on his way home, but sometimes it does!!)
It gets as sophisticated as you want it to. And another thing -- your VOICE also communicates. Like when I said above that mine know "Excuuuuuuse me?? I don't THINK so!!" -- do they understand those individual words? No .. they understand my inent -- because when I say "Excuse me Pardon me!!" that means move your buns outa my way!!
And yeah, when they move I say "thank YOU!!" and they know that means a job well done but something I expect TO be done so there's no huge effusive praise due.
They are like a blank page and they will learn all you teach them.
I also teach mine sign language from the instant they come in here. So I can say "I love you!!" from 100 feet away and get wriggles and wags!! I can also say "SHHHH" and have them shut up!!
Signs and words -- they are just more commands, just more language. They learn what they are taught so they can better communicate with us.
But do your dog a favor -- learn to listen to THEM too. Watch their ears, their head, their body language -- they WILL talk back to you .... if you listen. *smile*