I'd the line Is straight, speed is constant. If it is bent in anyway, It is non constant
It varies. The planets move in their orbits at different distances from the sun and at vaying speeds. The distances between them is constantly changing.
A thyristor is a "triggered" device. It will remain off until its gate electrode is made to conduct. It will then stay on (showing a very low resistance) until the power is removed, or (in Gate Turn Off devices) until a turnoff voltage is applied. A transistor can be used as a variable-resitance element. While it can be made to switch (like a thyristor) it does not need any special turn-off: just remove the input signal and it will go open circuit. A transistor can be made to respond to a vaying input signal with a varying resistance, so it can be used as a linear (analogue) amplifier.
There are over 400 different pasta shapes ranging from Long pasta much like spaghetti and vaying from there to be thinner or thicker or hollow or ridged. Then there are short cut pastas like Ziti or Rigatoni. These are also, hollow, solid, ridged, flat surface and some that are even completely flat. Stuffed pasta shapes such as ravioli and tortellini. Soup pastas or pastina such as alphabets, stars and orzo which is pasta shaped like rice. The list goes on and on and you could literally eat pasta every day for a year and not have the same pasta shape twice.