Well, I'll begin in an alphabetical order and ommit the names which are very simmilar (for example: eng. basilisk - sp. basilisco) however, if it is completely different in, lets say french (I really don't know if it is the case), feel free to add it to the list.
If you want to add the translation in your language try to keep at least the number of the english word, so you don't have to write it again - for new words, keep adding numbers. (for example: 16. gr/dt Feuerblitz)
I think, the easiest way to find the terms is to use the search menu on the explorer window (ctrl+F, for example).
Feel free to make any corrections!
If you ask yourselves what's the goal of this dictionary: I think it is a help for those, who don't know what a particular word means or how they have to translate the word in english, because they didn't read the books in english. On the other hand, you can always learn some words in other languages, thats fun for some people, I think .
It is not a problem if you only add one or two words, because everybody might find them by searching the original english word or the corresponding number.
1. Baron, the Bloody sp. El Varón Sanguinario
2. Beater sp. bateador
3. Bertie Bott's Every Flavor Beans sp. grageas Bertie Bott de Todos los Sabores
4. Blast-ended screwts sp. Escregutos de cola explosiva
5. Bubotubers sp. bubotubérculos
6. Canary cream sp. galleta de canario
7. Chaser sp. cazador
8. Chocolate frogs sp. ranas de chocolate
9. Curse sp. maldición
10. Daily Prophet sp. periódico/diario El Profeta
11. Dark Mark sp. Marca tenebrosa
12. Death Eaters sp. mortífagos
13. Diagon Alley sp. callejón Diagon
14. Fat Friar sp. Fraile Gordo
15. Fat Lady sp. Dama Gorda
16. Firebolt sp. Saeta de Fuego
17. Floo Powder/Network sp. polvos/red de polvos Flu
18. Foe-Glass sp. detector de enemigos
19. Forbidden Forest sp. Bosque prohibido
20. Gillyweed sp. branquialgas
21. Goblet of fire sp. Cáliz de fuego
22. Grey Lady sp. Dama Gris
23. House elf sp. elfo doméstico
24. Howler sp. vociferador
25. Invisibility cloak sp. capa de invisibilidad
26. Keeper sp. portero
27. Knight Bus sp. autobus Noctámbulo
28. The Leaky Cauldron sp. El Caldero Chorreante
29. Mandrake sp. mandrágora
30. Marauder's Map sp. Mapa del Merodeador
31. Moaning Mirtle sp. Mirtle la Llorona
32. Mudblood sp. Sangre sucia
33. St Mungo's Hospital for Magical Maladies and Injuries sp. Hospital San Mungo de Enfermedades y heridas Mágicas
34. Nick Nearly Headless sp. Nick Casidecapitado
35. O.W.L.s /owl sp. TIMOS /lechuza
36. Pensieve sp. pensadero
37. Pocket sneakoscope sp. chivatoscopio
38. Polyjuice potion sp. poción multijugos
39. Portkey sp. traslador
40. Quick-quotes quill sp. pluma vuelapluma
41. Remembrall sp. recordadora
42. Secrecy Sensor sp. Sensor de ocultamiento
43. Seeker sp. buscador
44. Shrieking Shack sp. casa del los gritos
45. Sorcerer's Stone sp. piedra filosofal
46. Sorting Hat sp. Sombrero seleccionador
47. S.P.E.W. sp. PEDDO
48. The Three Broomsticks sp. Las Tres Escobas
49. Ton-Tongue Toffee sp. Caramelo Longuilinguo
50. Unforgiveable Curses sp. Maldiciones Imperdonables
51. Wormtail sp. Colagusano
If anyone knows if it's possible to put an excel like grid on a post, please tell me. (TABs didn't work, so I put between the words)