A conjunction is a word used to join two parts of a complex sentence. Many English language sentences include conjunctions. While "but," "that," "or," "because," and "since" are all common conjunctions, "and" is the most often used, according to the Corpus of Contemporary American English, a 450-million-word collection of written texts.

Statistics

As of a summer 2012 review, the Corpus Of Contemporary American English indicated 10,741,073 uses of "and" within its expansive collection. This amounts to roughly 2.4 percent of all words, making "and" the third most common word in the English language. "That" was the second most common conjunction, but it appeared roughly one-third as often as "and," with only 3,430,996 uses. "But" was third most common with 1,776,767 appearances.