Capsid is a term commonly used in virology to refer to the protein coat surrounding a virus. However, there are several synonyms for this term depending on the context. For instance, in some literature, the term "protein shell" is used instead of capsid. The term "proteocapsid" is also used in some cases to describe the combination of the protein shell and the viral genome. Additionally, the term "nucleocapsid" is used to describe the capsid with the viral nucleic acid inside. Overall, these various synonyms can be used interchangeably, but it is essential to understand the context in which they are being used.