Which of the following terms is used to describe the outer layer of a virus containing the capsid?

The outer layer of a virus containing the capsid is referred to as the envelope. The envelope is typically a lipid membrane that surrounds some viruses, providing them with additional protection and allowing them to enter host cells more easily through processes like fusion with the host membrane. This lipid bilayer can often be derived from the host cell's own membrane as the virus buds off, and it usually contains viral proteins that are essential for infection and interaction with host cells.

The capsid, which is composed of protein subunits called capsomers, serves primarily to protect the viral nucleic acid and is crucial for the structural integrity of the virus. While both the envelope and the capsid are vital in virus structure, the envelope specifically refers to the additional outer layer found in some viruses, distinguishing it from the capsid itself.