"I am behind her."
Translation:Táim taobh thiar di.
There are a couple of other ways to say 'behind somebody/something', depending on the exact context. You can say 'ar chúl +gen' ('+gen' meaning a noun in the genitive case) or 'i ndiaidh + gen', though this latter one is closer in meaning to 'after somebody/something'.
So you could say 'táim i do dhiaidh' for 'I am after you' or 'táim ina chúl' for 'I am behind him'. 'ina' isn't a typo, by the way, but one of the rare exceptions to the usual 'broad with broad, slender with slender' spelling rule and means 'in his/her/their'.
taobh means "side" and thiar primarily means "west" but it also implies "back" or behind, because when you are looking at the rising sun, the West is at your back/behind you.
Here are some other examples of phrases used "behind" or "at the back of":
Ar an taobh thiar den teach - "At the back of the house"/"Behind the house". Taobh thiar aniar - "back to front"
Tá na súile thiar ina cheann - "his eyes are sunk back into his head"
Taobh thiar den bhalla - "behind the wall"
Thank you. I find the use of West for behind so interesting. I found your examples interesting as well but I guess my question was do you need both words to "taobh" and "thiar" together if you are meaning the English word of "behind" and are they used all the same ways that we use "behind"?