Latent defect - These defect are unidentified bug which are existing in the system over a period of time. The bug may exist in the system for one or more versions of the software and may also be identified after its release.
Masked defect – It is the defect which is hiding the other defect, which is not detected. That means if there is an existing defect which is not found to reproduce another defect. The second defect is being masked by the first one.