Correct

一天

/ yī tiān / 
Strokes

Definition

one day

Example

As a Noun

a day

1
Yī
一
tiān
天
yòu
又
yī
一
tiān
天

day after day

As a Noun

the whole day; all day long

2
Yī
一
tiān
天
dīshuǐ
滴水
wèi
未
jìn
进

have had nothing the whole day

As a Noun

one day (in the past)

3
Yī
一
tiān
天
  
,
tā
他
tūrán
突然
huílai
回来
le
了
  
。

One day, he came home unexpectedly.