Quote Originally Posted by zorro View Post
Is нa a preposition in Вадим старше меня нa год? In English I would think of it as "by one year". Why is it stressed unlike other prepositions? Are there other examples of this in Russian? Is there any underlying rule that might help me?
I agree with what It-Ogo wrote about the stressed prepositions. I just want to add something more on it.

1) This question has been asked several times on this forum. Try searching some older threads on stressed prepositions. Unfortunately, I do not remember what were the thread titles. If I find any, I'll provide you with links.

2) You can also try googling if you are interested in this phenomenon. For example,
https://www.google.ru/?gws_rd=cr#new...w=1280&bih=570

Particularly, you may read this discussion Stress shifting from noun onto prepostion - WordReference Forums.

3) Unfortunately, there is absolutely no rule for this. You cannot predict this shift from the word itslef. However, in modern language it mainly happens is some fixed expressions or fixed combinations. And you will be still understandable if you do not follow those combinations.

4) Some examples which come to my mind right now:
(взять/схватить) зА руку, (взять/схватить) зА ногу, с ног нА голову, смотреть пОд ноги, поехать зА город (meaning "to go to the countryside") although many would pronounce "за гОрод", бЕз толку, задание нА дом (home assignment)... There are many others.