手早い答え
causal は因果、casual は偶然・時折・非公式に関係します。
確実な見分け方は、英語から訳す前に、その単語の働きを見きわめることです。
それぞれの単語の働き
causal
causal
Use causal for relating to a cause-and-effect connection.
casual
casual or by chance
Use casual for happening occasionally, informally, or without prior planning.
選び方
- causal: Choose causal if the sentence points to relating to a cause-and-effect connection.
- casual: Choose casual if the sentence points to happening occasionally, informally, or without prior planning.
例文
O estudo não provou uma relação causal.
The study did not prove a causal relationship.
Foi um encontro casual no aeroporto.
It was a chance encounter at the airport.
よくある落とし穴
A correlação causal explains why something happens. A coincidência casual simply happens without planning.
文脈の中で練習する
自分の実生活から文を一つ選び、二回書いてみましょう。一度はcausalで、もう一度はcasualで。どちらも成り立ちそうなら、意味の違いを言葉にしてみましょう。