A。いわんや B をや / においてをや

[Needless to say / Not to mention (literary)]

Connection: Statement A。いわんや B をや

Usage: A highly literary and classical expression equivalent to まして(や). Means "needless to say" or "how much more/less so for B." Derived from classical Japanese 言わんや (wouldn't one say?). Used in formal writing and speeches.

Examples:

プロでさえ失敗する。いわんや素人においてをや。(Even professionals fail. Needless to say, amateurs even more so.)

親ですら理解できない。いわんや他人をや。(Even parents can't understand. Not to mention strangers.)

国内でも問題だ。いわんや国際社会においてをや。(It's a problem even domestically. Needless to say, in the international community even more so.)