mindmap root((TETR)) tetracycline A yellow broad-spectrum antibiotic.
🌱He was sent home with a prescription for tetracycline and some advice about how to avoid Lyme disease in the future. 🌳Most chemical names are made up of two or more Greek and Latin roots strung together. Thus, tetracycline, with its cycl- root from the Greek word for "circle," means "four-ringed"—that is, "consisting of four fused hydrocarbon rings." Antibiotics work against bacteria and other tiny organisms （but not viruses）; tetracycline, which comes from a kind of soil bacteria, is one of the most used of the antibiotics. "Broad-spectrum" antibiotics work well on numerous organisms; thus, tetracycline has proved effective against acne, chlamydia, cholera, rickets, and various lung and eye infections, among many other conditions. tetrahedron A solid shape formed by four flat faces.
🌱Her son's box kites was a tetrahedron, and its pyramid shape was easy to pick out among the traditional designs flown by the other children. 🌳The simplest tetrahedron is made of four equal-sided triangles: one is used as the base, and the other three are fitted to it and each other to make a pyramid. But the great pyramids of Egypt aren't tetrahedrons: they instead have a square base and four triangular faces, and thus are five-sided rather than four-sided. tetralogy A set of four connected literary, artistic, or musical works.
🌱The Raj Quartet, Paul Scott's long and complex tetralogy of India, was made into a highly praised television series. 🌳Vivaldi's Four Seasons could be called a tetralogy, since it's a set of four violin concertos, one for each season of the year. Eight of Shakespeare's history plays are often grouped into two tetralogies. Wagner's great Ring of the Nibelung, an opera tetralogy based on Norse mythology, contains about 18 hours of music. The original tetralogies, however, were sets of four plays by the same author performed together in ancient Greece; the first three were always tragedies, and the last was a wild comedy. Tetralogies were written by such great dramatists as Aeschylus, Sophocles, and Euripedes; unfortunately, none of them have survived in their entirety. tetrapod A vertebrate with two pairs of limbs.
🌱His special study was the great seismosaurus, probably the largest tetrapod—and the largest land animal—that ever lived. 🌳The earliest tetrapods, or "four-footed" animals, were mammal-like reptiles that evolved before the rise of the dinosaurs and ranged from mouse-sized to cow-sized. Today the tetrapods include the reptiles, the amphibians, the birds, and the mammals—including humans. Though the fish aren't classified as tetrapods, it's quite possible that our own limbs began as paired fins hundreds of millions of years ago.