preposition

mit

with

Dieses Wort zeigt, dass etwas zusammen oder gemeinsam mit einer anderen Person oder Sache geschieht.

The German preposition mit is one of the most fundamental words in the language. It translates primarily to "with".

Accompaniment or Association: It denotes being in the company of someone or having something along. (e.g., "Ich gehe mit meinem Freund" - I am going with my friend).
Instrument or Means: It is used to describe the tool, method, or means by which an action is performed. (e.g., "Ich schreibe mit einem Stift" - I am writing with a pen).
Manner: It describes the way in which something is done. (e.g., "Er antwortet mit Freude" - He answers with joy).
Time/Start: In some contexts, it indicates the starting point of an action or a recurring event. (e.g., "Mit dem neuen Jahr..." - Starting with the new year...).

Grammar:

mit is a dative preposition. This means that any noun or pronoun following "mit" must be in the dative case.
It is often used to form common contractions, such as "mit dem" becoming "mitten" (though this is less standard than "im" or "am") or in phrases like "mitnichten" (by no means).

Word origin:

mit originates from the Old High German word "mit", which traces back to the Proto-Germanic "*midi". It is etymologically related to the English word "mid" (as in "midst" or "midway").