Vowel whose quality does not change over the duration of the vowel is called a monophthong. Monophthongs are sometimes called "pure" or "stable" vowels. A vowel sound that glides from one quality to another is called a diphthong, and a vowel sound that glides successively through three qualities is a triphthong. All languages have monophthongs and many languages have diphthongs, but triphthongs or vowel sounds with even more target qualities are relatively rare cross-linguistically. English has all three types: the vowel sound in "hit" is a monophthong , the vowel sound in "boy" is in most dialects a diphthong , and
Types of plant oils Types of plant oils Plant oils or vegetable oils are oils derived from plant sources, as opposed to animal fats or petroleum. There are three primary types of plant oil, differing both the means of extracting the relevant parts of the plant, and in the nature of the resulting oil: Vegetable fats and oils are what are most commonly called vegetable oils. These are triglyceride-based, and include cooking oils like canola oil, solid oils like cocoa butter, oils used in paint like linseed oil and oils used for industrial purposes. Pressed vegetable oils are extracted from the plant containing the