Certainly
Surely
adverb
This is an adverb, but it has the same meaning (basically) as the kanji. It means certainly, and it can also mean surely.
The reading for this one is certainly weird. To remember the reading for this word, just think how you're certain that if you stash the treasure, nobody will find it here.
コウイチが百メートルほど飛ぶのを、この目で確かに見ました。
I'm certain I saw Koichi fly about one hundred meters with my own eyes.
この機械をそう作するのは確かに難しそうだね。
It seems like it might be difficult to operate this machine.
確かにトーフグは、伝統的な日本語学習業界にダブルパンチを食らわせました。
Tofugu has certainly delivered a one-two punch to the traditional Japanese language learning industry.