In biology, a host is an organism that harbors a parasite, mutual partner, or commensal partner, typically providing nourishment and shelter. See host (biology) for detail and also symbiosis.
A host may also be a group, such as an army or a large number of people under a single cause or banner. The typical usage in English is like "a host of US troops invaded Iraq in 2003". In the Bible, expressions like the heavenly host mean "chorus or army of angels". This is using a similar definition of host.
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