確かに[tashikani] surely
確かめる[tashikameru] to ascertain
確言[kakugen] assertion
確乎[kakko] firm
確執[kakushitsu] discord

確実[kakujitsu] certainty
確実性[kakujitsusei] certainty
確実度[kakujitsudo] certainty
確証[kakushou] positive proof
確信[kakushin] conviction