first-class; top grade; primary
Used for ranking, quality, or level, often in formal or evaluative contexts such as exams, products, or skills.
This product was made by a first-class engineer.
He has first-class skills.
This tea is a top-grade product.
He has a reputation for having first-class skill.
This Japanese paper is regarded as top-grade.
一流 emphasizes being top-ranked in a field or among establishments/people, while 一級 focuses on grade or level within a formal ranking system.
最高 means 'the best' in an absolute, superlative sense, whereas 一級 signals a high position within a graded scale.
高級 stresses luxury or high price/quality (e.g. 高級レストラン), while 一級 is a more neutral grading term used in exams, certifications, or product standards.
特級 denotes a 'special grade' that often ranks even above 一級 in certain formal classification systems (e.g. sake grading).
二級 is the 'second-class' or lower grade directly below 一級 in ranked systems like exams, licenses, or product quality.
Compound of 一 (one, first) and 級 (grade, rank). The meaning is transparent from its components.