The engineering world is full of terminology that might confuse the uninitiated. Sometimes the words engineers use have a visual connection with something else and, in a way, when they start talking about male and female connections or nipples the connection is there although (maybe) we would rather not dwell on it.
Nipples
A nipple is a short length of pipe (often no more than an inch or so – depending on the pipe diameter) with external male threads at each end. In pipe or hose fitting jargon, a part that sticks out is male whereas the part with the hole that the male connects into is called the female. Thus, the male threads on the nipple ends can be screwed into internally threaded (female) openings in two other pieces of pipe so as to join them together. Usually the center portion of the nipple will be machined into a hexagonal shape like a night so that the nipple can be held by a regular spanner when the female part is being screwed onto it.
Hoses
With Brass Hose Nipples, the nipple is made of brass. Metals like brass are sometimes made into hoses but most hoses are produced in more flexible materials like rubber of other polymers. (The rubber hose may be reinforced with textile threads or metal wires and might have a braided metal cover that could be brass wire). With plain rubber hoses, the open ends of the hose are often forced over a slightly tapered male end and clamped or clipped in place to join them to some other piece of equipment or component part.
However, hoses that have an outer braid of metallic wire (for extra strength) will normally have a female component affixed to each end. Usually the end fixing is like a nut which mates with the threaded male end of a nipple or similar threaded fitting.
Brass
Brass is an alloy of copper with zinc although small amounts of aluminum, tin, iron, silicon and manganese are often added to provide required features (such as sea water resistance) in the finished alloy. Although similar to bronze, it should not be confused with that historic alloy. Brass fittings are common in many domestic applications and are also important for use in hazardous environments where sparks cannot be tolerated because explosive or flammable gases may be present (such as the fuel lines from your propane tank to your furnace). Hence, if your hose has a brass covering and end fittings you should also use Brass Hose Nipples.