noun, noun which may take the genitive case particle 'no'
first class; first rank; first place; first prize
Used for being in the top class or rank, or for winning first place or first prize. Common in compounds and phrases such as 一等賞 and 一等の席.
My younger sister won first prize in the lottery.
I reserved a first-class cabin.
one degree; one level; one grade
Counts a difference of one rank, grade, or level, often with 上がる, 下がる, 上, or 下. In many everyday contexts, 一段 or 一つ上・下 may sound more ordinary.
This year's rice dropped one grade from last year.
Adverbial use before adjectives or evaluative expressions, meaning much the same as 一番. It is understandable but less common than 一番 in modern everyday Japanese.
Of these, this one is the best.
I came in first place in the marathon.
The temperature rose by one degree.
He is the strongest.
I received first prize in the contest.
prime location; best district; excellent piece of land