Trace gas Trace gas The most abundant gases in the atmosphere are nitrogen (78.1%), oxygen (20.9%), and argon (0.934%). Combined, oxygen, argon, and nitrogen make up 99.934% of the gases in the atmosphere (not including water vapor). The other gases that are not part of the 99.934% of the atmosphere are called trace gases. The abundance of a trace gas can range from a few parts per trillion (ppt) by volume to several hundred parts per million by volume (ppmv). When a trace gas is added into the atmosphere, that process is called a "source". There are two possible types of sources
Most common words in Spanish includes samples from all Spanish-speaking countries. The list of "1000 most frequent word forms" comes from an analysis of CREA version 3.2. Plurals, verb conjugations, and other inflections are ranked separately. Homonyms, however, are not distinguished from one another. CREA 3.2 was published in June 2008. In 2006, Mark Davies, an associate professor of linguistics at Brigham Young University, published his estimate of the 5000 most common words in Modern Spanish. To make this list, he compiled samples only from 20th-century sources—especially from the years 1970 to 2000. Most of the sources are from the 1990s. Of the 20 million