Kimball Biology 5e says
Coelom is the main body cavity of many animals. It is lined with an epithelium derived from mesoderm.
Gilbert Embryonal Biology 9e says
Coelom is the space between the somatic mesoderm and splanchnic mesoderm that becomes the body cavity. In mammals, the coelom becomes subdivided into the pleural, pericardial, and peritoneal cavities, enveloping the thorax, heart, and abdomen, respectively.
Then my lecture materials and the research site say
Coelom is the secondary body cavity.
Finnish Wikipedia says that Coelom is only with invertebrates. Again the Wikipedia page about peritoneum suggests that human has abdominal cavity and no coelom, and other mammalians coelom.
Does human have Coelom?
The confusing thing is the use of the word "OR", since I am not sure whether people are using it in different pages like "XOR" or like "AND" in normal speaking.