Infill is a term commonly used in urban planning to refer to the development of empty or under-utilized spaces within already established areas. However, there are several synonyms for this word, which can be used interchangeably depending on the context of the sentence. Some of these synonyms include intensification, densification, redevelopment, renewal, and revitalization. These words highlight the importance of utilizing available land and resources in order to accommodate growing populations and minimize urban sprawl. By using these words, urban planners can effectively articulate their vision for creating sustainable and livable communities for all.