The root meaning of the word 'prefix' is 'sub-creation'. Its job is to form new words. The prefixes have no meaning of their own , but they combine with other words to express special meanings. Remember , prefixes are always added before the main word. For example - 'rate' is a word. The words uphar , ahar , prahar , bihar are formed by adding the prefixes sub , a , pra , b , respectively. In this way the vocabulary of Bengali language has been enriched by forming new words with the help of prefixes. Therefore , some prepositions are added before nouns or participles to form new words and change the meaning , these are called prefixes. The characteristic of the prefix is the prefix that is added to the beginning of the word or metal. The prefixes have no meaning of their own , but when added before other words they have the semantics or ability to create new words. Symptoms do not change because they do not have a declension or suffix. For this reason, in Bengali grammar, prefix is also considered as preposition. The characteristics of the symptoms are given below: 1. Symptoms have no meaning of their own. 2. It forms new semantic words. 3. These cannot be used independently in sentences. 4. These give fullness to the meaning of the word. 5. These sit before the nouns and participles. . Symptoms cause the word to expand , change, or shrink.