noun, used as a prefix
type 1; category 1; first class
Used as a prefix to classify something as the first type or category, often in technical, regulatory, or formal contexts.
第一種電気工事士の資格を取った。
I obtained a Type 1 electrician license.
この薬品は第一種指定化学物質に該当
This chemical falls under Class 1 designated chemical substances.
Means 'one kind' or 'a type', but not necessarily part of a numbered series like 第一種.
Compound of 第一 (first) and 種 (type, kind). The reading いっしゅ reflects a common sound change from いち + しゅ.