Synonyms by Category:
Action:
* Begin - Commence, Start, Initiate
* Stop - Halt, Cease, Terminate
* Look - Observe, Gaze, Examine
Feeling:
* Happy - Joyful, Cheerful, Delighted
* Sad - Depressed, Melancholy, Sorrowful
* Angry - Furious, Enraged, Indignant
Appearance:
* Beautiful - Gorgeous, Stunning, Exquisite
* Ugly - Hideous, Repulsive, Disgusting
* Large - Huge, Immense, Enormous
General:
* Good - Excellent, Wonderful, Fantastic
* Bad - Terrible, Awful, Horrible
* Easy - Simple, Straightforward, Effortless
* Difficult - Hard, Challenging, Demanding
* Important - Crucial, Vital, Essential
* Small - Tiny, Miniature, Minute
* Fast - Rapid, Swift, Speedy
* Slow - Leisurely, Gradual, Plodding
* Think - Consider, Ponder, Reflect
* Say - Tell, State, Declare
More specific examples:
* Brave: Courageous, Bold, Daring, Valiant
* Clever: Intelligent, Bright, Sharp, Astute
* Wealthy: Affluent, Rich, Prosperous, Opulent
* Hungry: Starving, Famished, Ravenous, Voracious
* Tired: Exhausted, Weary, Fatigued, Spent
* Funny: Humorous, Amusing, Hilarious, Comical
* Quiet: Silent, Still, Peaceful, Serene
* Angry: Furious, Enraged, Infuriated, Livid
Note: Synonyms are not always perfect replacements, as their nuances and connotations may differ. The context in which you use them is key to choosing the most appropriate word.