I know some of full-grown adults who say 'veggies'. I find it really irritating. NB The abbreviation 'veggie' can also mean 'vegetarian'. 'What's for lunch?' 'Chicken curry' 'What's the veggie option?' 'Veggie curry.' Other (fairly British) abbreviations that come to mind are 'pressie' and 'cardi'. Plus some that we've got from Australians - 'barbie' and even 'rellie'. Can you guess what those words are short for, Emarbe?

Hi emarbe, these shortened forms can be used in casual conversations, but most (not all) shortened forms are considered informal and should not be written in any formal documents. Since English is always changing, new shortened forms of words show up constantly. A good example is the word "dis," which means "to insult" (for example: "I can dis you at any time simply by calling you a coward!"). It's shortened from "disrespect." I hope I've at least partially answered your question. I know you said "for foreigners," but everyone struggles to pronounce English in different ways.

'Comfy' is used frequently. I'll be honest, the only person who I have ever heard say 'veggies' is my Spanish friend from Barcelona. Well, actually she does the typical thing that native Spanish speakers do where they don't distinguish 'b' and 'v' so it sounds like 'beggies.' I don't think I've ever heard a native speaker say it. It sounds a bit 'hippyish' to me. Or maybe something you might say to a child. I mean, 'vegetables' is not a hard word for natives to say. What people from the UK do though is shorten it to 'veg.' That is a much more natural shortening to me than saying 'veggies.' 'Fruit and veg' is a common thing to hear.

Yes, you can use them, but it depends on the context. If you're having a formal conversation, then I would advise not shortening your words. In fact, people shorten the first word even more. Often I hear just "veg" to refer to vegetables. Others I can think of are "admin" for "administrator," "legit" for "legitimate" (which is used so much I've actually met people who don't know that "legitimate" is where the shorter form comes from), "uni" for "university," "rehab" for "rehabilitation," and the list goes on. Take a look: https://www.englishclub.com/ref/Slang/Shortened_Words/ By the way, we spell "comfy" with a "y." :)