Abstract: A number of articles in some Chinese scientific journals used the terminology of “middle-deep lacustrine” in recent years, and the usage frequency is increasing. Based on analysis of the context, we propose that the so called “middle-deep lacustrine” belongs to the category of sedimentology under geology, and is equivalent to deep lacustrine(or semi-deep lacustrine and deep lacustrine). “middle-deep lacustrine” itself is literally unclear. No article has proposed the definition of “middle-deep lacustrine”, and no textbook has presented the words of “middle-deep lacustrine”. “middle-deep lacustrine” is definitely a false terminology and should be out of usage. The normative and traditional terminologies of “deep lacustrine” and “semi-deep lacustrine” should be continually used.

Key words: “middle-deep lacustrine”, semi-deep lacustrine, deep lacustrine, sedimentology, geology