一つ置きに

ひとつおきに

alternately

一人一人

ひとりひとり ひとりびとり

one by one, each, one at a time

一人ずつ

ひとりずつ

one by one; one at a time; in turn

一人きり

ひとりきり

all on one's own

一人歩き

ひとりあるき

taking on a life of its own (of a rumour, etc.)

一人にする

ひとりにする

to leave (someone) alone; to leave to oneself; to leave (someone) be

二つに一つ

ふたつにひとつ

one of two (possibilities, alternatives, etc.)

娘一人に婿八人

むすめひとりにむこはちにん

being besieged by suitors; to be popular; eight suitors for one daughter

一つには

ひとつには

for one thing...

万に一つ

まんにひとつ

one in a million (chance, etc.); one in ten thousand; in the unlikely event that

一人

ひとり

one person

選手一人一人

せんしゅひとりひとり

each athlete

一人っきり

ひとりっきり

all on one's own

一人一票

ひとりいっぴょう

one person, one vote

一人前になる

いちにんまえになる

to come of age, to become an adult, to become fully qualified, to stand on one's own

一人悦に入る

ひとりえつにいる

to be pleased with oneself, to chuckle with delight

一つ一つ

ひとつひとつ

one-by-one, separately, in detail

一つ置き

ひとつおき

alternate, every other one

一つ書き

ひとつがき

an item, itemization, itemisation