He is experiencing the difficulties of puberty.

According to Freud's theory, the phallic stage is a part of a child's sexual development.

Infancy is an important period for human growth and development.

I am a new student of this school.

He missed a once-in-a-lifetime opportunity.

"Once in a lifetime" means to cherish the encounter that happens only once in one's lifetime.

During the dry season, it is important to conserve water.

What is the half-life of this substance?

His dog is currently in its sexually active period.

They have been in a good relationship since old times, always spending time together.