See virion.
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cap·sid 'kap-səd n the protein shell of a virus particle that surrounds its nucleic acid
cap·sid·al -səd-əl adj
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cap·sid (kapґsid) [L. capsa a box] the shell of protein that protects the nucleic acid of a virus; it may have helical or icosahedral symmetry and is composed of structural units, or capsomers. According to the number of subunits possessed by capsomers, they are called dimers (2), trimers (3), pentamers (5), or hexamers (6).
Electron microscopy and computer-generated three-dimensional image reconstructions of several icosahedral capsids showing the capsid symmetry and the individual capsomeres. (1), Equine herpesvirus nucleocapsid; (2), simian rotavirus; (3), reovirus type 1 virion; (4), reovirus intermediate subviral particle; (5), reovirus core (inner capsid) particle; (6), human papillomavirus type 19 (papovavirus); (7), mouse polyomavirus (papovavirus); (8), cauliflower mosaic virus. (Bar equals 50 nm.)
Medical dictionary. 2011.