That depends on your definition of "language", where some definitions are much more scientifically useful than others. Defining language as "a system of communication" is not very useful, since there are important defining characteristics most people, and especially most linguists, believe that language possesses that other more general forms of communication do not.
Under the definition used by most linguists (for the kind of object we're talking about here, that is - there are many other relevant objects of study that can be called a "language"), spoken/signed human languages have all of the characteristics of language, while "body language"/animal "languages" do not.
Sign language is language, since it has a systematic, unconscious mental grammar that meets all of the characteristics above, and writing is not considered language, since it's just a means of encoding/preserving a language that already exists.
Another way of stating this is that writing is not itself the output of a mental grammar - it's the output of a translation algorithm that acts on the output of a grammar, and so can't be considered language itself (again, under one of the most common definitions of "language" used in the scientific study of human language).
I agree that it has to do with definition. My definition of language might be of a wider range than yours (and linguists)
My cat, for example, might not use grammer but I can certainly communicate with her (and she with me!) In this sense she and I have a language between us that's a mix of signs, sounds, and body language. It's not possible for me to seperate our talks from language, even though our understanding of each other doesn't cover specifics.
So if someone communicates with me via emoji, and I understund accurately, I would count it as language (even if it goes against classical definitions)
What would you say about a dog growling at you, communicating its displeasure at how close you are? If you back away, understanding what the dog intends to convey with its growl, does that make the dog's growl language?
Is a honeybee secreting a pheromone to get the hive to swarm language?
If so, how is language meaningfully different from "communication"? And, is human communication with each other the same type of phenomenon as the cases you and I mentioned, or is there some sort of categorical difference there?
(Also, this definition isn't classical - it's quite modern. The tendency to conflate writing with language in cultures that have writing is as old as writing is, and disentangling the two is a relatively modern discovery.)
Lemmy's being difficult for me (or it could be Connect for Lemmy) so I keep having to find the post in order to reply to you! (Meaning I might have to stop replying, but if I do that's why)
And yes, I would say a dog growling and a honey bee releasing pheromones are also examples of language! I'm sure many would disagree (and rightfully) but my general perspective on the matter is that any type of communication is language (but I can see how it can be argued that no, it's not language which is different- they're just so closely related in my mind that to me they're practically synonyms)
Ok, strictly speaking, the language is called the Egyptian language and hieroglyphs were the writing system used to write it (until Greek influences evolved it into Coptic). But that's an extremely pedantic distinction to anyone who isn't a linguist.
Writing isn't language at all, for reasons discussed in my comments below.
Which is part of what makes linguistics work on ancient languages so difficult - we're having to use these imperfect symbols, which themselves aren't language, to try to glean as many features about the actual grammars they're intended to represent, which are language.
This is why we know much less about ancient languages than we do modern ones - because we have actual recordings of modern languages (the recordings themselves are also not language, of course; they just encode language much better than writing does), so we can get at many more features of the language in question.