Ooh! This is actually an interesting question! First I'll write a sentence using each one, and then I'll try to write out simple explanations for them. We went to our respective houses. That is a very respectable action. He is respected in his community. Be respectful to your elders! Okay. Now for the explanations. I'm making this, like I just said, very simple. If I went into really detailed grammar rules, I'd probably lose you, and it's best for you to have a natural ear for a language anyway (as opposed to mechanically applying rules to your speech). "-ive" refers generally to direct (usually possessive) objects. It's used to distinguish between several objects that are owned by different subjects. Hence, when I say, "We went to our respective houses," what I mean is, "I went to my house, and they went to their house." "-able" refers to a noun's capacity for being whatever the adjective defines. It's literally ABLE to be that word. So when I say, "That's a very respectable action," I mean, "Your action is capable of being respected." "-ed" refers to a noun's quality. Unlike "-able", where the modified noun is able to be seen as something, "-ed" means that it literally IS something. So when I say, "He is respected in his community," I mean, "He is a man with respect in his community." "-ful" refers to how a noun acts. It is literally "full" of whatever verb the adjective is based off of (and is thus interchangeable with that verb). So when I say, "Be respectful to your elders," I am saying, "Respect your elders." I can simplify it even more if you are confused; just tell me to do so and I'll try my best.