Common words:
* Submarine: A vessel that operates underwater.
* Submerge: To go under water.
* Subsequent: Following in time or order.
* Substitute: A person or thing that takes the place of another.
* Subtitle: Text that appears on screen to translate dialogue.
* Subway: An underground railway system.
* Suburban: Relating to a residential area on the outskirts of a city.
* Subtropical: Relating to a climate zone between the tropics and the temperate zones.
Less common words:
* Subcontract: To hire someone to do part of a job.
* Subcutaneous: Situated or occurring beneath the skin.
* Subdivision: A smaller part of a larger area.
* Subdue: To conquer or overcome.
* Subliminal: Below the threshold of conscious perception.
* Submerge: To go under water.
* Subordinate: A person of lower rank or status.
* Subsidize: To provide financial support.
* Subterfuge: Deception used to achieve a goal.
* Subversive: Seeking to undermine or overthrow an established system.
Words from different fields:
* Subatomic: Relating to the particles that make up atoms.
* Subgenus: A taxonomic rank below genus.
* Subspecies: A taxonomic rank below species.
* Sublimation: A process in which a solid changes directly into a gas.
* Subculture: A smaller group of people within a larger culture.
* Sublimation: In psychology, a process of transforming unacceptable impulses into socially acceptable behavior.
This is just a small sample of words starting with "sub." The prefix "sub" is very versatile and can be used to create many different words with a variety of meanings.