Data can be segmented into minimal units. Such a process is called base segmentation. In this chapter, I discuss three types of base segmentation of language data, depending on its three media types: phoneme segmentation, image segmentation, and text segmentation. They can be grouped into larger units. Base segmented text, for instance, undergo tokenization, annotated segmentation such as word segmentation, and chunking with POS-tagging. The semantic annotation of language data, whether written, spoken, or visualized, requires the target data to be segmented and preferably annotated with appropriate morpho-syntactic information.