1.
one person
The counter for one person, using an irregular reading.
一人 uses an irregular native Japanese reading (not いちにん). It means "one person" and also "alone."
IRREGULAR COUNTING:
- 一人: one person
- 二人: two people
- 三人: three people (regular from here)
COMMON EXPRESSIONS:
- 一人で: alone, by oneself
- 一人暮らし: living alone
- 一人旅: solo travel
- 一人前: one serving; fully-fledged adult
- 一人っ子: only child
NOTE: 一人で can imply doing something independently (positive) or being lonely (context-dependent).