Auxiliary verb
(those) who are; (that) which is; in the capacity of
after a noun, usu. as 〜たる者, etc.; often used in relation to qualifications and requirements for a positionsee たりsee たるや
アメリカ人たる私は、リンカーンがすばらしい人だと思う。
I, as an American, admire Lincoln.