Can we say a sentence without subject?

Question

I saw a sentence (or phrase or whatsoever, I'm not sure) in a comment of a native speaker in the comment section on F*cebook.

Here's the sentence, by the way:

Now your just being patronising.

If I categorize the segments of the sentence, my first guess would be (Firstly, I might be wrong) :

• Now is a conjunction [now (that)].

• your just being patronising is (I don't know what it is called, but I think it acts like a noun)

Describing the second highlighted point above, what I mean by acts like a noun is, for example, there's a sentence:

I don't like his borrowing my things without asking.

The bold type can be thought as a noun, like when I substitute them with something:

I don't like something.

Let's back to my main question. Where's the subject? Can I say or write something like this, I mean if my prediction is correct, doesn't the sentence above have the same sense as we say [now + noun]? Like when I say: {now milk, now candy, now banana, now chocolate}. My big point, is it grammatically fine to use that as a sentence? Unlike the sentence I've given as an example, it doesn't have a subject, in my view.

Or is it just common writing/saying or did she misspell you are and wrote your instead? Because I've seen some people do that. If so, then it has a subject and please confirm this assumption. I've read this, by the way: when-is-a-gerund-supposed-to-be-preceded-by-a-possessive-adjective-determiner

Answer 1

Although traditional grammar says that sentences require a subject and a verb, this isn't true of all sentences. For instance, I could say "Hello", "Thanks", "OK", "Yes". Some of them might count as interjections, but not all. Then there are phrases like "Once bitten, twice shy", although you could argue that there are words that are "understood", so that the full phrase is "Once you've been bitten, you're twice shy", even though we'd never say that and it actually sounds awkward.

In the case of your example:

Now your just being patronising

This is a full sentence, but it's misspelt, as you suspected. The correct spelling is:

Now you're just being patronising.

where "you're" is a contraction of "you are". So there's a subject ("you").