in thea place that is being or has been now departed from

I've left the keys behind

in, to, or towards the back

Look behind

in a secondary or inferior position

(usu + in/with) in arrears

He is behind in his payments

(usu + with) late

I've got behind with my work

remaining after (somebody who has departed)

He left a great name behind him

obscured by (something)

There was malice behind the mask of friendship

less advanced than

behind the rest of the class

not keeping up with

behind schedule

in the background of (something)

the conditions behind the strike

in support of (somebody or something)

solidly behind their candidate