What is the difference between pipe, tube and a conduit?

Tube and pipe are for conveying liquid and/or gases under pressure. The main difference between the two is how they are sized. Pipe is sized according to a nominal ID(inside diameter) while tube is sized according to its OD ( outside diameter) Another difference is that pipe is rigid while tubing may be either rigid or flexible conduit - although similar to a pipe or tube is not rated for the conveyance of liquid or gases but rather used for protecting and routing electrical wiring. 

they are all similar... depending on the applications, we will tend to use one term rather than the other.  I would suspect some people could differentiate with size: a tube could have a diameter smaller that the pipe's one, being smaller that the conduit's one.

They all are Similar but depends on their size. if a hollow circular thing is available having very less diameter made up of glass then it will be called a tube where in pipe the Diameter is little more or we can say more than 10 mm. Diameter of Conduit is more than pipes.

PIPES AND TUBES ARE FULLY ROUND SHAPE, CONDUIT IS HALF ROUND SHAPE

pipes & tubes are the same and (closed) with the difference size

conduites are opened

 pipe , tube and conduits are the same thing but  the deferance is thier sizes

also the materials that made from it.

Hose is for hand cleaning

Tube is used for a connection or a small connection not too long

Conduit is used for shipping or injection and it is used for a long distance

Try this link http://pipinglearning.blogspot.qa/2012/07/difference-between-pipeline-piping.html

which may  give fair idea for your question.

Thanks

they are used to transfer from one place to another but differential in sizes

pipe and tube are meanly not similar, however, pipes are almost circular shapes but the tube is almost square.