Efficient everyday communication and the need of members of every speech community to use linguistic means of expression to affirm their identity and thus confirm their belonging to a certain area or social group represent the most prominent incentives for the birth of city speech. These are urban idioms which originate as a consequence of a spill­over and intertwining of linguistic phenomena with nonlinguistic ones, resulting from a sudden growth in size and role of cities in contemporary society. The interspersing of regional, i.e. dialectal characteristics with elements of standard language under the influence of social factors in the conditions of strong urbanization, results in the birth of a speech which features a suppression of less prestigious characteristics of organic idioms and their replacement by innovative ones. The adaptation of language to the needs of urban culture, i.e. the ability of language to keep pace with changes in the social life of a speech community which uses it, most frequently involves its opening towards the influences of prestigious foreign languages and the activation of its own expressive possibilities, which contributes to the speed and ease of communication. Such circumstances produce speeches characterized by lexical productivity and innovativeness, semantic expressiveness, metaphoricity and associativeness, as well as a ludic play with meaning. Although the lexical stock of the Croatian language is unquestionably most frequently expanded by formal word formation, far more ingenuity is shown in the case of adding new meanings to existing lexical units, i.e. “old” words, which, are often overlooked, due to their inconspicuousness on the formal level. The lexicon, as the most flexible part of language, especially its semantic layer, readily answers to any change in human activities in any sphere of life. Having this in mind, this paper will pay special attention to semantic shifts involving no change in expression, i.e. no interventions into the morphological composition of lexemes typical of the Osijek city speech. To this end, a survey on 100 subjects was conducted. The survey included only those native inhabitants who have lived in Osijek since birth. These were divided into two age groups with an equal number of subjects: 50 subjects aged 15­25 and 50 subjects aged 45­55. The study included subjects of different social and economic status and education. Special attention was paid to including an equal ratio of subjects of both genders and age of speakers. It is assumed that this would more clearly show tendencies in semantic formation, and flesh out the vocabulary which changes from that which is constant in meaning and use. The interpretation of results aims to illustrate mechanisms which dominate in semantic shifts and test whether there is difference in age in their use. Furthermore, the effects of semantic formation are also discussed, as is the extent to which it contributes to the economy, flexibility and expressiveness with which speakers of the Osijek urban community express their extralinguistic experiences on a daily basis.