Among the selection criteria for the new polyurethane were that the material exhibited a combination of good wear characteristics and mechanical properties, was easy to handle, and provided for fast, easy alteration and repair of polyurethane as well as metal patterns.
A linguistic universal is a pattern that occurs systematically across natural languages, potentially true for all of them. For example, All languages have nouns and verbs, or If a language is spoken, it has consonants and vowels.
The term linguistic variation (or simply variation) refers to regional, social, or contextual differences in the ways that a particular language is used. Variation between languages, dialects, and speakers is known as interspeaker variation. Variation within the language of a single speaker is called intraspeaker variation. Since the rise of sociolinguistics in the 1960s, interest in linguistic variation (also called linguistic variability) has developed rapidly.