Basic Forms:
* arch: (adjective) Chief, main, important.
* arch: (noun) A curved structure, often supporting a bridge or doorway.
Derived Words:
* archangel: (noun) A chief angel, often considered to be a very powerful angel.
* archaeology: (noun) The study of past peoples and cultures by examining their material remains.
* archbishop: (noun) The chief bishop of a province or church.
* archduke: (noun) A prince of high rank, usually a ruler or heir apparent.
* archenemy: (noun) A chief enemy or rival.
* archetype: (noun) A perfect example or model of a person or thing.
* architect: (noun) A person who designs buildings and other structures.
* architecture: (noun) The art or science of designing buildings.
* archive: (noun) A place where historical documents or records are kept.
* archway: (noun) A covered passageway formed by an arch.
* architrave: (noun) The lowest part of an entablature, resting directly on the columns.
Phrases:
* arch-conservative: (adjective) Extremely conservative.
* arch-villain: (noun) A main villain or antagonist in a story.
* arch-rival: (noun) A main rival or opponent.
* arch-traitor: (noun) A main traitor.
Let me know if you'd like more examples!