the first in grade or rank

a day or two / today or tomorrow / tomorrow or the day after tomorrow

one small animal

one dog

One slice or cut of something.

in ancient China, the paperboard on which the imperial decree was written, or the imperial decree

Used other than figuratively or idiomatically: see 一, 発. / doing something only once / (baseball, informal) home run

task; (doing a) bit of work / difficult task; hard work

(slang) the only choice, the one possible option

a surname