What is a system of spelling in which each sound represented by single character?

A system of spelling in which each sound is represented by a single character is called a phonemic orthography.

Here are some key features of a phonemic orthography:

* One-to-one correspondence: Each sound in the language has its own unique written symbol.

* Transparency: It's relatively easy to learn how to read and write because the spelling directly reflects the pronunciation.

* Regularity: There are few exceptions to the spelling rules.

Examples of phonemic orthographies:

* Finnish: It's known for its highly regular and predictable spelling system.

* Esperanto: This constructed language was designed with a phonemic orthography.

* IPA (International Phonetic Alphabet): This system uses one unique symbol for each distinct sound in all languages.

Note: While phonemic orthographies are designed to be consistent, they are not perfect. Even in languages with highly phonemic spelling, there can be some exceptions or inconsistencies.