A preposition describes a relationship between words in a sentence. Prepositions are nearly always combined with other words in structures called prepositional phrases. Prepositions like in or after are rather meaningless and hard to define in mere words. The use of the right preposition after certain verbs often gives much difficulty. In everyday speech, we fall into some bad habits of using prepositions, where they are not necessary. It would be a good idea to eliminate these words altogether. But we must be careful especially not to use them in formal and academic prose. However when using the idiomatic phrases, which in turn uses different prepositions, one has to take care, not to omit, any one of them. Thus the correct usage of prepositions and prepositional phrases is discussed in this page, with an objective to eradicate the ambiguity arising with the improper use of prepositions.