Why do we say 'I like dogs'? Why can't we say 'I like dog' if we are referring to a particular dog? Most people use 'I like dogs'. Which is correct and why?
"I like X" suggests you like the stuff of X. When it is an animal, the implication is that you like to eat it. Thus, "I like dog" sounds like dog as a food.
"I like Xs" suggests you like things of the X type; thus for animate objects it suggests you enjoy spending time with them, so "I like dogs" suggests you like them as pets.
"I like this X" is entirely context dependent. "I like this chicken" when at a petting zoo would mean you think it is a friendly chicken, but at a meal table would mean you think it is tasty.
"Dog" is a count noun, and you mean you like dogs in general (i.e., more than one dog), so you'd use the plural form.
If you were talking about a noncount noun such as coffee or luggage or research, you'd say "I like coffee/luggage/research."
Native speakers usually know intuitively which nouns are count nouns. Generally, count nouns are things that are considered to be possible to count, like dogs or chairs or people. Noncount nouns are things that are too abstract or numerous to count, like enjoyment or sand. It's possible to imagine contexts in which noncount nouns become countable (e.g., in a restaurant if you are ordering specific dishes from a menu, you might count them: "3 beefs, 2 turkeys") but your "I like X" is not one of those contexts.
It depends what you are referring to!
if you are referring to Dog as an animal you say:
I like dogs. (meaning all dogs/dog varieties).
If you have been talking about a specific Dog (your dog or neighbour's). You might wanna say:
I like that dog.
If you are comparing animal species (talking biology or some zoology stuff). you might wanna say:
I like dogs and you ?
depends on what you are talking about!