確実, かくじつ
NA-adjective
certain, sure, definite, reliable, sound, solid, safe, secure
これは遅いけど確実な方法だ。
だ
Auxiliary verb, copula, See である, See です, plain copula
be, is
た, だ
Auxiliary verb, だ after certain verb forms; indicates past or completed action
1. did, (have) done
indicates mild imperative
2. (please) do