noun:the number 1
I have one apple left.
pronoun:referring to a person or thing previously mentioned or easily identified
If anyone calls, tell them I’m not home; I’ll call one back later.
adjective:used to indicate a particular but unspecified thing
One day, I will travel the world.
noun:a single unit or entity
They are a team, acting as one.
adverb:once or on a single occasion
He has travelled to Japan one time in his life.
pronoun:used to refer to people in general
One should save regularly for emergencies.
adjective:in agreement
The board was of one mind about the plan.
noun:a person or thing considered first in rank, importance, or preference
She remains the team's number one.
