to be about or relate to (something or somebody)
The novel concerns three soldiers
to involve or have an influence on (somebody)
The problem concerns us all
to be a cause of trouble or distress to (somebody)
His ill health concerns me
to engage or occupy (oneself)
He concerns himself with trivia
as far as somebody or something is concerned
with regard to somebody or something
to whom it may concern
used at the beginning of a letter that is not addressed to anybody in particular
[Middle English concernen via French from medieval Latin concernere, from con- + Latin cernere to sift]