The word mit can exist as preposition,
Ich fahre mit dem Auto. Ich werde mit dem Auto fahren.
I drive by car. I will drive by car.
literal: I drive with the car. I will drive with the car.
Das Hemd gehört mit in die Wäsche. Das Hemd wird mit in die Wäsche gehören.
The shirt also belongs in the laundry. The shirt will also belong in the laundry.
literal: The shirt cobelongs in the laundry. The shirt will cobelong in the laundry.
and as prefix of a separable verb
Ich fahre mit wenn ich Zeit habe. Ich werde mitfahren wenn ich Zeit habe.
(Sorry, I have no Idea how to properly translate this into valid English)
literal: I coride when I have time. I will coride when I have time.
(Instead of "co-ride" maybe also "co-go" or "co-drive")
In the examples above I use the prefix co- in the sense of "worker and co-worker" or "driver and co-driver."
The prefixes of separable verbs are closely related to adverbs, and when those verbs are split in their parts, it is often hard to tell if it is an adverb or a split-off prefix. And also the meaning in both functions is almost identical. Both, the adverb "mit" and the prefix "mit" mean:
to do something together with someone else
Here is a simple example:
If you walk, it is
Du gehst. = You walk.
If I walk, you have
Ich gehe. = I walk.
Du gehst und ich gehe.
You walk and I walk.
But if you deside where to go to, and I accompany you, i.e. I walk on your side and you decide where to got to, then it is:
Du gehst und ich gehe mit.
You walk and I co-walk.
This construction doesn't exist in proper English, so I use this co- prefix to express what is meant in German. And this co- prefix works for both, the adverb mit and the separable prefix mit.
This verb means:
- to listen (to hear something and pay attention to it with the intention to hear it)
- to overhear (to hear something by accident, without having wanted to hear it)
But there is also a third possibility: You didn't want to hear it (i.e. it was not your intention to listen), so you overheard he conversation. But after you heard a few words you became curious and payed attention, so you turned from overhearing to listening. In German all of those is:
ein Gespräch anhören
to overhear or listen to a conversation
When two people chat in a room, and when there is a third person in the room who can hear the conversation, you can say:
Walter hört das Gespräch von Erich und Brigitte an.
1. Walter listens to the conversation of Erich and Brigitte.
1. Walter overhears the conversation of Erich and Brigitte.
In English you have to make a difference, if Walter is listening intentionally, or if he is overhearing the conversation by accident. In German you don't make this difference. Without context it is to listen, i.e. to pay attention to the conversation, but without initial intention. If you want to clarify the difference, you have to tell it explicitly in a separate sentence.
When Erich talks to Brigitte, Brigitte is listening. And when Brigitte talks, Erich is listening. These two persons are the main-listeners. And if another person joins the club of listeners, then this person is co-listening or co-overhearing.(remember: both is the same word in German: anhören)
So, when you realize that Lisa and Sandra also overhear this conversation, then they co-overheard the conversation:
Lisa und Sandra hören das Gespräch mit an. Sie werden das Gespräch mit anhören.
Lisa and Sandra co-overhear the conversation. They will co-overhear the conversation.