let understand about the lightweight, dead weight and displacement of the ship

Lightweight :

• Is defined as just empty bare weight of the ship.
• Let's say that we are building a new ship.
• The entire weight of the ship without any consumables light fuel oil, lube oil, stores, supplies, spares, crew. The bare weight of the ship is called the light weight.
• We can count every machinery, tanks, pipelines, as lightweight. accept the consumbles like lube oil, fuel oil, inventory, fresh water, etc,.

Deadweight :

• Let's say , empty ship put out in water. The ship sinks of certain draft. This sinkage is due to lightweight or weight of the empty ship without any stores, fresh water, fuel oil, lube oil.

Now to understand the deadweight,

• We are going to feel the ship with necessary supplies, let say spares per engine, freshwater fuel oil, cargo and inventory. When we feel the ship with all these necessary supplies for the learning of the ship.
• Dead weight consist of cargo, freshwater, lube oil, fuel oil, inventory, spares,

Displacement :

• When as ship of light weight put out in water it sings to certain draught, let's say 'd'.

Lightweight - d = empty ship.

• Upon the lightweight, the dead weight is added to ship change the draught to D.

Now, 

Displacement = dead weight - D =empty ship + dead weight.

There fore , 

displacement = dead weight +lightweight.

• Take bucket full of water, we are going to drop a ball.
• Let say ball as weight 'w' and thus weight is added on water.
• We know the water exerts the optimist opposite direction equal to the weight of the ball.
• Due to the weight of ball the water steps to spill out of bucket. The weight of ball displaces equal amount of water and when you collect the displaced water in a beaker, if you measure the weight of water in beaker it will be equal to the weight of ball.