traditional ordering of the Japanese syllabary; iroha order
Refers to the classical poem-based ordering of kana, often used as a framework for listing or categorizing things.
Please arrange them in iroha order.
fundamentals; the ABCs of ...
Used figuratively to mean the basics or rudiments of a subject, similar to 'the ABCs' in English.
First, I want to learn the ABCs of economics.
This book teaches you the fundamentals of cooking.
I memorized the iroha ordering when I was a child.
He doesn't even know the basics of computers.
五十音 is the modern, systematic ordering of kana used in dictionaries and textbooks, while いろは is the older poem-based ordering now mostly used for decorative lists or numbering items.
Rare kanji form; it is rarely used.
Rare kanji form; it is rarely used.