The word "berth" is a nautical term that has several meanings, four of which are nouns that apply to cruise ships and/or commercial marine ships. Many people confuse the spelling of the terms "birth" and "berth", but they have different definitions. The origin of the term "berth" is obscure, but many experts believe it comes from Middle English.
Dock or Pier
First of all, berth refers to a dock, quay, or pier where a ship ties up. It can also be called a mooring. A berth is similar to a parking spot for a car--it's the place where the ship is "parked". Oftentimes, the port authority assigns a berth to a ship, much like an allocated parking place.
Many cruise travelers do not realize that mooring berths aren't free; cruise lines must pay for parking at the pier just like drivers have to pay for parking their cars in a lot. The longer a ship stays in port, the more the berthing fee is. If your cruise ship stays in port longer or has many ports of call, the basic cruise fare might be higher. This is one reason why repositioning or transatlantic voyages with many sea days are often cheaper--the cruise line doesn't have to pay many port fees and pass the cost along to its passengers.
Giving up Space
The second definition of the term berth is the space one ship gives to another. For example, one ship will give another a wide berth, which means that the ship is avoiding the other ship by providing it plenty of space to maneuver. This wide berth can be for safety or convenience. Although this is originally a nautical term, the idiom "give a wide berth" has made its way into common English usage to relate to avoiding anything, person, or place. It especially is important when someone is in a bad mood!
A Place to Sleep
The third definition of berth relates to a bed or sleeping space. Most often, berth relates to a shelf-like or pull-down bed on a ship. These built-in beds are small since they were first designed to fit in tiny cabins like on the sailboat seen in the photo. However, cruise ships usually use the word berth to mean a bed on any type on the ship. So, although berth started out as a built-in shelf or bunk, it now can also mean a single, double, queen or king-sized bed on a cruise ship.
A Job on a Ship
The fourth definition of berth describes a job on a ship. This definition also probably relates to the number of beds (berths) on a ship since each employee needs a berth. Therefore the number of berths (jobs) would equal the number of berths (beds). Merchant marine ships use the term more often than cruise ships do since each berth on a cruise ship does not match specifically with a job.