Is to a prepossission

The phrase "is to" can be interpreted as a preposition in some contexts, particularly when indicating a relationship or direction, such as in "is to be" or "is to come." However, it is more accurately described as a verb phrase or part of a larger construction rather than a standalone preposition. In English, prepositions typically include Words like "in," "on," "at," and "to," which show relationships between nouns and other elements in a sentence.