The Education Bureau informed all schools that it is a sick sentence to ask principals to report their work on Friday. Ill sentences refer to faulty sentences, and all sentences that violate grammatical structure rules or objective facts are ill sentences. The former is called grammatical error and the latter is called logical error. The common types of ill sentences are: improper word order, improper collocation, incomplete or redundant components, disordered structure, unclear meaning, illogical, ambiguous, mixed sentences, improper classification, and one-sided (double-sided/single-sided).