Languages have different levels of othographic depth, that means that a language’s orthography can vary in a spectrum of a very irregular and complex orthography (deep orthography) to a completely regular and simple one (shallow orthography).
English, French, Danish, Swedish, Arabic, Urdu, Tibetan, Burmese, Thai, Khmer, Lao, Chinese, and Japanese have orthographies that are highly irregular, complex and where sounds cannot be predicted from the spelling. These writing systems are more difficuld and slow to be learned by children, who may take years. In the medium of the scale there’s Spanish, Portuguese, German, Polish, Greek, Russian, Persian, Hindi, Korean, where there are some irregularities but overall the correspondence of one sound to one phoneme is not that bad. At the positive end of the scale there’s Italian, Serbo-Croat, Romanian, Finnish, Basque, Turkish, Indonesian, Quechua, Ayamara, Guarani, Mayan languages, and most African languages (because there were no history of spelling, so a new one of scratch was made as very regular), they all have very simple and regular spelling systems, with usually a one-to-one correspondence between sounds and letters. These are very easily learned by children.
Note: remember that there’s no objective numbering on the three categories I made, there are more than just these three categories, because it works like a spectrum. Three categories were used just as a means for simplification.
