Inventory
The οriginal Esperanto lexicon contains 24 consonants, including 4 affricates, one, /x/, which has become rare, and one, /w/, which is only found in onomatopoeia and in foreign names; and 11 vowels, 5 simple and 6 diphthongs. A few additional sounds in loan words, such as /ou̯/, are not stable.
Read more about this topic: Esperanto Phonology