In 1983, the metre was redefined in the International System of Units (SI) as the distance travelled by light in vacuum in 1/ 7008299792458000000â 299792458 of a second. As a result, the numerical value of c in metres per second is now fixed exactly by the definition of the metre.
Blattodea is an Order of insects containing the cockroaches. Cockroaches first evolved around 350-300 million years ago and are probably one of the most despised of all insects. For some people the mere mention of cockroaches will send them running for cover.
The noun mulatto is an old-fashioned way to refer to someone with one black parent and one white parent. It was common to describe a mixed race person as a mulatto during the period of slavery in the United States. If you use the word mulatto to describe someone of mixed race, most people will know what you mean, but they may also be offended. People of mixed race are much more likely to describe themselves as biracial than mulatto these days.