Body language that exist in all languages. Body language, on the other hand, does not have a grammar system and must be interpreted broadly, instead of having an absolute meaning corresponding with a certain movement, so it is not a language like sign language, and is simply termed as a "language" due to popular culture. In a community, there are agreed-upon interpretations of particular behavior. Interpretations may vary from country to country, or culture to culture. On this note, there is controversy on whether body language is universal. Body language, a subset of nonverbal communication, complements verbal communication in social interaction. In
Wide-body aircraft wake turbulence is generally related to the weight of an aircraft, these categories are based on one of four weight categories: light, medium, heavy, and super. Due to their weight, all current wide-body aircraft are categorized as "heavy", or in the case of the A380 in U.S. airspace, "super". The wake-turbulence category also is used to guide the separation of aircraft. Super- and heavy-category aircraft require greater separation behind them than those in other categories. In some countries, such as the United States, it is a requirement to suffix the aircraft's call sign with the word "heavy" (or "super") when