• rhe rubicon,
• fhe rubicon,
• ghe rubicon,
• yhe rubicon,
• 6he rubicon,
• 5he rubicon,
• tge rubicon,
• tbe rubicon,
• tne rubicon,
• tje rubicon,
• tue rubicon,
• tye rubicon,
• thw rubicon,
• ths rubicon,
• thd rubicon,
• thr rubicon,
• th4 rubicon,
• th3 rubicon,
• the eubicon,
• the dubicon

The adjective form of the phrase "the Rubicon" is "Rubiconian".

The plural form of the word "the rubicon" is "the rubicons"

The singular form of the word "the rubicon" is "the rubicon". The word "rubicon" does not change in form when used in singular or plural.