What is another word for main-line?
Pronunciation: [mˈe͡ɪnlˈa͡ɪn] (IPA) 
Main-line, a compound word, carries several meanings. It can refer to the primary train route that connects major towns and cities; it can also refer to the principal method or system that a person or organization uses to accomplish its objectives. There are many synonyms for the word main-line, including; flagship, primary, central, core, essential, fundamental, key, leading, principal, primary, and vital. Each of these synonyms has a particular use and implies a slightly different meaning. For instance, the word "vital" can suggest that a system or method is indispensable, while "flagship" suggests that something is the most important part of a particular system or organization.
