Variety (Data in many forms).

These data do not have a fixed structure and rarely present themselves in a perfectly ordered form and ready for processing.

Indeed, such data can be highly structured (data from relational databases), semi-structured (web logs, social media feeds, raw feed directly from a sensor source, email, etc.) or unstructured (video, still images, audio, clicks).

Another “V”, for Variability, can be added to variety to emphasize on semantics, or the variability of meaning in language and communication protocols.