preposition
in or to a lower place than (something) :below or beneath (something) :underneath
guided or managed by (a person or group)
controlled or affected by (something)
in a particular state or condition :affected by a particular process
according to (something)
within the group that has (a particular title or label)
used to say that a particular name is used to indicate something
less or lower than (a certain age, amount of money, etc.)
hidden below (an outward appearance)
adverb
in or into a position that is below or beneath something
in a forward direction that passes below something
less than an expected or stated number or amount
into an unconscious state
go under