The language is a social phenomenon. It is in the most tightly relationship with the whole changes from the society. The vocabulary reflects the objective reality and records the new. The quantitative growing of the lexis depends on the internal means, through the formation of some words from the linguistic material existent, or through the external means, bz borrowings from other languages. The internal means should be more active than external means, because their function is a generative forming the essential in the language. The derivation with prefixes is one between the main methods of forming new words in Romanian language. Although the number of the Romanian prefixes is lower than the sufixes, in the last decades the linguists noted the growing of weight of prefixation in technical – scientific and publicist style.