X refers to the western medicine in the drug approval number before 2003.

x= 10

In Roman numerals, x stands for 10.

X stands for unknown or unknown things.

X-men English letters 19. It is often used in mathematics to represent unknowns. Kissing means, only for girls.

roentgen ray

Noun (short for noun)

X ray examination

Xanthate

Noun (short for noun)

Xanthate

Oxyanthracene

Noun (short for noun)

Two parallel books.

yellow

Adjective (abbreviation for adjective)

Yellow and white