Main
Principal
Synonyms: Principal, head, foremost, major, dominant, focal, prime, premier, first, grand, supreme, (most) prominent, paramount, cardinal, vital, capital, salient, essential, intrinsic, chief, leading, most important, ruling, central, key, master, primary, high, fundamental, predominant, pre-eminent, overriding, crucial, critical, pivotal, elemental, staple, and urgent.
Sea
Synonyms: Sea, deep, the drink, ocean, brine, and the briny.
Example Sentences
The main topic is science today.
He explained the main idea clearly.
The main event starts tomorrow afternoon.
She highlighted the main points carefully.