Dual refers to something in a pair. After you install the dual carburetors, open the throttle half way. Duel is a formal battle or contest intended to settle a dispute. “Duel of the Titans” is a film about Romulus and Remus.
Downfall refers to the destruction of something. The Russian Revolution led to Czar Nicholas II’s downfall. Drawback refers to a flaw or problem of some kind. Their plan to camp there had one drawback: too many gnats.
Down the pike is the correct phrase. It means something is going to happen. The Pike was originally a huge entertainment area at the 1904 St. Louis World’s Fair. Fair goers would commonly say, There’s always something new coming down the Pike.
Douse means to extinguish or wet thoroughly. The firefighters doused the flames with water most of the night. Dowse means to look for water or minerals with a divining rod. It was common for the pioneers to dowse for water on the trail.
Doubtful means to be uncertain. It’s doubtful if we will ever know who technically won the election. Dubious refers to doubt or uncertainty about something. The official gave a dubious reply when asked about the proposed tax cut.
Dominant means commanding or controlling over all others. The largest wolf is usually dominant in the pack. Dominate means to control, govern, or regulate something. Their software dominates the financial services industry. Domineer means to exercise arbitrary or overbearing control. The strong will of a few can sometimes domineer a community.
Dogmatic means arrogantly authoritative or overbearing. His dogmatic and demanding personality did not fit in well here. Pragmatic means practical. Pat takes a pragmatic approach to teaching children.
Dog-eat-dog-world is the correct phrase. It means that the world is ruthlessly competitive and derives from a sixteenth century proverb that people may revert to the animal laws of survival. With shrinking markets, it’s now a dog-eat-dog world for many companies.
Doctor refers to anyone who has been granted a doctor’s degree. Physician is a general term for a doctor of medicine, someone legally qualified to practice medicine. All physicians are doctors of medicine, but not all doctors practice medicine.