Lo siento vs Lamento
I wonder if you could use "Lo siento que" to mean I'm sorry that, or I'm sorry about or if it's just an interjection. "Lo siento que te hayas ido"..."Lamento que te hayas ido".. I think the latter sounds better, but I wonder if there are some circumstances where lo siento could replace lamentar, or if there is another good word for "I'm sorry".
Edit: I decided to add this awesome false cognate to the examples list. Decepcionar - to disappoint. Decepcionada = disappointed
Lo siento que te sientas decepcionada. Lamento que te sientas decepcionada.
2 Answers
I agree with Julian Chivas.
Don't put the "lo" in front of "siento" if you plan to say a compound sentence. If you say "I'm sorry", use either "lo siento" or "lo lamento", meaning "I regret it" or "I lament it".
On the other hand - "I am sorry that you might be sick" - "Siento/Lamento que estés enfermo" - I regret/lament that you might be sick. You don't want to mistakenly say the equivalent of "I regret it that you might be sick".
Good question.
Lo siento is used more for apologies and things of that nature.
Lamento is to express true regret, thus having a stronger feeling than "Lo siento."