Therefore
Consequently
conjunction
You learned that 故 means reason. Basically, whatever comes before 故に in a statement is going to be the reason for something that comes after. So 故に works like therefore or consequently. It can also be translated as "because" or other similar conjunctions depending on the context.
Also keep in mind that 故に is mainly used in formal contexts, like in academic writing or politicians' speeches — just like "therefore" in English.
By knowing the word 故 you'll know the reading for this word too! Here's a mnemonic in case you need a reminder, though:
You're using WaniKani, therefore you're studying kanji and vocab. Whose fault is it? It's WaniKani's fault! But, your brain has been beaten to a mush from all the studying, so when you say "it's your fault" it comes out as "it's yue fault!" Go ahead and say it out loud that way.
故に、この薬は人々に知られるようになったのです。
Therefore, this medication became known to the people.
私は美人が故に顔ばかり見られます。以前は嫌だったんですが、今は美人が故の宿命だと思って受け入れています。
As a consequence of being good-looking, people tend to only look at my face. I used to dislike it, but now I accept it as the fate that comes with being a beautiful woman.
「何が故にソナタたち人間は苦しむのじゃ？」「愛故に人は苦しまねばならぬのだ」
"Why do you humans suffer?" "It is because of love that humans must suffer."
度重なる無断遅刻故に、 休暇日数が減らされてしまった。
I was repeatedly late without permission and consequently my vacation days were cut short.