Prepositions in Greek are words that link nouns, pronouns, or phrases to other words in a sentence, indicating relationships such as direction, location, or time. Common Greek prepositions include σε (in, at), με (with), and για (for). They often require specific cases for the nouns they govern, such as the accusative, genitive, or dative. In Greek grammar, the use of prepositions can change the meaning of a sentence significantly. For example, the preposition σε can indicate movement towards a place, while από (from) indicates the origin of movement. Understanding these prepositions is essential for constructing clear and accurate sentences in Greek.