Particle is the opposite of Wave. Wave is related to Crash. Crash is related to Accident. Accident is a synonym of Chance. 
Vertical is related to Steep. Steep is a synonym of Plunge. Plunge is a synonym of Launch. Launch is a synonym of Throw. 
Particle <--Antonym--> Wave <--RelatedTo--> Crash <--RelatedTo--> Accident <--Synonym--> Chance 
Vertical <--RelatedTo--> Steep <--Synonym--> Plunge <--Synonym--> Launch <--Synonym--> Throw 