"In class of" can be replaced with various synonyms depending on the context. For instance, "category of" can be a suitable alternative for classification and grouping. "Type of" can be used to refer to a particular version or form of something. In contrast, "level of" is commonly used to indicate the degree of proficiency or difficulty in a subject matter. "Subset of" can refer to a smaller section or group within a larger one. "Kind of" can be a synonym for "in class of" when describing a general type or nature of something. Other synonyms may also be applicable depending on the context, and it is essential to choose the most appropriate one.