我十八岁。

I am eighteen years old.

I'm 18 years old.

I am 18 years old.

Source: Tatoeba

Sentence Composition

1 我 wǒ
  1. I
  2. me
  3. my
2 十八 shíbā
  1. eighteen
  2. 18
=3 岁 suì
  1. variant of 歲 suì, year
  2. years old
=3 岁 suì
  1. classifier for years (of age)
  2. year
  3. year (of crop harvests)