mainstay

noun

1. A chief support.

   “Agriculture is the mainstay of this country’s economy.”

   “At the other extreme, we have that true maid-of-all-work type, the 0-6-0, the mainstay of goods, shunting, and often of passenger work right from the earliest days to the present time.”

   “As with most other railways, freight revenue is the mainstay of the balance sheet. In Canada, passenger revenue is only about one-tenth that of freight.”

   “Oil is the mainstay of Nigeria's economy.”

   “Conventional radiography has a major role in, and remains the mainstay of, initial evaluation and follow-up of rheumatologic disease.”

2. Someone or something that can be depended on to make a regular contribution.

   “On the Bishops Stortford line, the crisis now seems to be over; the units designed for this service are the mainstay of the workings once again and although some of the inner suburban sets are still seen, very few L.T.S. Line units are noticeable.”

   “Afternoon TV mainstays like Leila Benitez and Bobby Ledesma of Darigold Jamboree gradually gave way to teenage loveteams Vi and Bot and Guy and Pip who had legions of fans watching their shows and movies and listening to their records.”

   “Like show dogs, dog actors became a mainstay in European and American contexts from the early nineteenth century with the convergence of public sentiment for dogs and popular interest in training them.”

   “The marina was a mainstay of the neighborhood, and Mr. O’Rourke was known for staging salsa and merengue concerts.”

   “Crickets are a mainstay of panfishing with live bait—and a mainstay of bait shops—but they come off the hook easily and you'll be plagued by minnows and tiny fish constantly stealing your bait.”

3. A stabilising rope from high on the mainmast to the base of the foremast.