"Ob" is a prefix derived from Latin, meaning "against" or "in the way of." It is commonly used in various English words to indicate opposition or obstruction. For example, in the word obstruct, it signifies blocking or hindering progress. In addition to its use as a prefix, "Ob" can also refer to a specific type of observation in scientific contexts, where it denotes a focus on particular phenomena. This term is often used in fields like astronomy and biology to describe the act of closely monitoring or studying specific subjects or events.