miteinander
with each other
Together; in a mutual relationship or action.
Die beiden Abteilungen müssen besser miteinander kommunizieren.
The two departments need to communicate better with each other.

with each other
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with each other
Together; in a mutual relationship or action.
Die beiden Abteilungen müssen besser miteinander kommunizieren.
The two departments need to communicate better with each other.

The word is a compound of the preposition 'mit' (with) and the reciprocal pronoun 'einander' (each other). So it literally means 'with each other' or 'with one another.'
Wir sollten offen miteinander über das Problem reden.
We should talk openly with each other about the problem.
As an adverb, 'miteinander' (with each other) usually comes after the conjugated verb and any objects. It describes how an action is carried out.
Die Teammitglieder arbeiten sehr produktiv miteinander.
The team members work very productively with each other.
'Miteinander' (with each other) is often used with verbs that express a mutual action or relationship. Typical examples are: 'miteinander reden' (to talk with each other), 'miteinander arbeiten' (to work with each other), 'miteinander auskommen' (to get along with each other), or 'miteinander Zeit verbringen' (to spend time with each other).
Es ist wichtig, dass Nachbarn gut miteinander auskommen.
It is important that neighbors get along well with each other.
In this meaning, 'miteinander' (together) is often used with verbs such as 'verbinden' (to connect), 'vermischen' (to mix), or 'kombinieren' (to combine). It emphasizes that different elements are joined into a whole.
In dem Rezept werden Mehl und Zucker zuerst miteinander vermischt.
In the recipe, flour and sugar are first mixed together.
together
'zusammen' and 'miteinander' both fit when several people do something together. Often, the two words can be used in similar ways. However, 'zusammen' is more general: people can work together, live together, or simply be together in one place. 'miteinander' puts more emphasis on the relationship or mutual action, for example speaking, discussing, or playing. They can be confused because both mean 'not alone'. As a practical guide: for a shared activity, 'zusammen' often fits; for an action between people, 'miteinander' sounds especially natural.

Die Nachbarn sprechen wieder freundlich miteinander.
The neighbors are speaking to each other in a friendly way again.
Nach der Arbeit kochen wir heute zusammen.
After work, we are cooking together today.