Both mean that a person is relunctant to spend money. Stingy is more commonly used as an insult. Cheap is also a slightly negative word, but it's one that people would be more likely to use to describe themselves. ("I can't go; I'm so cheap.") It's also the word that people would use to make fun of someone in a joking way (between friends, "Oh come on, don't be so cheap!") "Frugal" is a positive way to say it. If you admire someone's caution with money, you would say they're very frugal. Be careful when you use cheap because it can also mean someone who doesn't value herself when it comes to sex (like "Don't go out in that dress - it makes you look so cheap.")

To get under someone's skin means that you're annoying someone. Ex. "He just gets under my skin -- I really hope he doesn't come tonight." I've never heard the phrase used any other way, like to say "I've got you under my skin." I suppose that's just a playful use of language that turns a negative statement into something that sounds positive... I wouldn't just throw it around -- you would be misunderstood! ;)

I should clarify that I'm trying to learn how to speak in directives for the purpose of talking to my 3 year old and 2 year old in Arabic. I want to play a game like "Run!" "Jump!" "Sit!" etc. I also want to know how to change verbs into the command form just for the sake of understanding the language better. (I would not just go up to someone in Arabic and say "Drink!" or "Eat!") ;)

Most people use the term to talk about a person's appearance. If you want to use the word in reference to a person's personality, you wouldn't just say "She's very attractive" -- you would say "Her sense of humor makes her attractive" or "She's so compassionate; I find that really attractive." The default is looks unless something else is specified.

Mohamed, forgive me for sounding stupid, but are you asking because you want to kill yourself??? :( Or are you for some reason looking for terms related to suicide?

It means that you thought it through and decided it was a bad idea. Ex: I was going to hitch-hike the rest of the way, but I thought better of it. You changed your mind and decided not to do what you were about to do.

A colectivo is a city bus, the kind you hop on as it rolls to an almost-stop at the intersection. They're chalk-full of people, loud, with poor shocks, and fun to ride. :) A van is called a furgoneta (when it's a mini-van). A camion is a large truck or sometimes a bus, but it's more normal to call a bus that isn't a colectivo an autobus (accent on the u of bus). Most trucks are called camionetas. Hope that helps!