In English, the term "vowel" is often used to refer to vowel letters even though these often represent combinations of vowel sounds (diphthongs), approximants, and even silence, not just single vowel sounds (monophthongs). Most of the present article is concerned with the length of vowel sounds (not vowel letters) in English. Even classroom materials for teaching reading also use the terms "long" and "short" in referring to vowel letters, while confusingly calling them "vowels". For example, in English spelling, vowel letters in words of the form consonant + vowel letter + consonant ("CVC") are called "short" and "long" depending on whether or not they are followed by the letter "e" ("CVC" vs. "CVCe") although those vowel letters called "long" actually represent combinations of two different vowels (diphthongs). Thus a vowel letter is called "long" if it is pronounced the same as the letter's name and "short" if it is not. This is commonly used for educational purposes when teaching children.