いっしゅ一種isshuひとくさ一種hitokusa
1.
A term used to refer to a single type or category of something, often indicating a specific grouping based on shared characteristics or features.
2.
A phrase used when acknowledging that, while something may not fit neatly into a certain classification, it can still be considered part of that group when focusing on particular attributes.
3.
An expression that conveys an indistinct or vague sense that something possesses a unique or particular quality, even if it cannot be explicitly defined.
Example:
イルカは哺乳類の一種です。