Pitaya is just an alternate spelling of the more common pitahaya which is most commonly called dragon fruit (also strawberry pear).
The foodlywise website about dragon fruit explains health benefits of dragon fruit, how to grow dragon fruit and history of dragon fruit.
http://dragon.fruit.pitaya.fruit.foodlywise.com/
There is not difference other than the name between pitaya and pitahaya or dragon fruit.
pitaya
Dragon fruit is just a common name for pitaya which is also called pitahaya or strawberry pear. There is no difference between the plant itself. There are just several names for the same plants.
The scientific name would be Selenicereus megalanthus.
Different cultivars of pitaya are red- or yellow-skinned; the internal part may be white or red.
cacti bear edible fruit such as the prickly pear and hylocereus which produces dragon fruit or pitaya.
Sinaloa is the name of a state in western Mexico. Its state capital is the city of Culiacan, but its most important urban area is the resort city and port of Mazatlan, with shores on the Pacific Ocean.Sinaloa comes from the language of the Cahita people, who inhabited those lands before contact with Europeans was established; it means "Round pitaya"; Pitaya is the fruit of a cactus common to the Americas and southeastern Asia, which is also known as the dragon fruit.
Some Mexican fruits starting with 'P' would include:Platano (banana)Piña (pineapple)PapayaPera (pear)Pistacho (pistachio)Pomelo (grapefruit)Pitaya
Dragon fruit can be called Hylocereus cacti, pitaya, pitahaya, fire dragon fruit, dragon pearl fruit, green dragon, or strawberry pear.
Dragon Fruit (Pitaya or Pitahaya) can be planted at any time. Spring and Fall are suggested as the best time of year, but other months work, also.
By consuming 100g almonds we will get 705 mg of potassium, banana, apricot, avocado, pitaya, grapes, dates are some other good sources for potassium.
You can buy it online and from some plant nurseries.
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern --T-YA. That is, six letter words with 3rd letter T and 5th letter Y and 6th letter A. In alphabetical order, they are: pitaya