one(adjective)

1 in number

one person; He took one book.

one(noun)

the number or figure 1

One and one is two (1 + 1 = 2).

one(pronoun)

a single person or thing

She's the one I like the best; I'll buy the red one.

one(adjective)

aged 1

The baby will be one tomorrow.

one(noun)

the age of 1

Babies start to talk at one.

one(pronoun)

anyone; any person

One can see the city from here.

one(adjective)

of the same opinion etc

We are one in our love of freedom.