The term 'LAB RODENT' is a combination of two words, 'RAT' (3 letters) and 'LAB' (3 letters). The term refers to a type of rodent that is used in laboratory experiments. Rats are often used in scientific research due to their small size, low cost, and ease of handling. They are also used in medical research, as they are able to mimic many human diseases. Rats are also used in behavioral studies, as they are able to learn quickly and remember what they have learned.