A semivariogram is a tool used in geostatistics to analyze spatial patterns and variability in data. It measures the similarity or dissimilarity between pairs of data points at different distances and directions, and it is commonly used to model the spatial correlation structure of a variable. There are several synonyms for semivariogram, such as spatial autocorrelation function, spatial covariance function, variogram, and covariance function. Each term emphasizes a different aspect of the method, but all refer to the same concept of measuring the spatial dependence of a variable. Ultimately, the choice of terminology depends on the field of application and the specific context of the analysis.