In the United States you are considered a grown-up when you reach the age of 18. You are no longer legally connected with your parents, and you are entitled to the rights—and expected to fulfill the duties—of an adult American citizen. (You may vote and be called for military service, for instance.)
There is a good chance, though, that when you are 18 your body has not yet reached full maturity. Many people continue to grow for a few more years. Most are fully grown—at least in height—by the time they are 20 years old, though boys may keep on growing until they are 23.
Yes. Not all plants are seed plants. Some plants, such as ferns and mosses, reproduce with spores instead of seeds. Spores, like seeds, can survive harsh conditions and develop into new plants. However, unlike seeds, spores are produced without fertilization and contain neither a plant embryo nor endosperm. Some plants can reproduce without spores or seeds through vegetative reproduction, in which a part of the stem or root gives rise to a new plant.
The term B.C. stands for “Before Christ,” and is used to date events before the birth of Jesus Christ. A.D. is the abbreviation for the Latin phrase anno domini, which means “in the year of our Lord,” and is used to date events after Jesus’s birth. This system of dating has been used for many years by Western archaeologists. Today, however, with a growing understanding that not all archaeologists are Christians, some archaeologists prefer to use the terms B.C.E. (meaning Before the Common Era) and C.E. (meaning Common Era). These terms are exactly the same as B.C. and A.D., but are not related to Christianity.
Absolutely! Strong, healthy teeth help you speak clearly, chew harder vegetables and meats, and help you look your best. Brushing your teeth helps prevent plaque, a clear film that sticks to your teeth. The sticky film acts like a magnet for bacteria and sugar. Bacteria eats the sugar on your teeth, breaking it down into acids that deteriorate tooth enamel, causing holes called cavities. Plaque also causes the gum disease gingivitis, which make your gums red, swollen, and sore. At around age six, you lose your baby teeth and a larger set of teeth begin to surface. Eventually, 32 new teeth will line your growing jaws, the last coming in around the age of 18.
These permanent teeth will perform all of your eating tasks for the rest of your life, so they are worth taking care of! Your four front teeth (on top and bottom) are sharp incisors that cut and tear off food when you bite, along with your four pointed canine teeth. The flat-topped bicuspids (premolars) and molars near the back of your mouth crush and chew your food.
A bilingual person is able to speak two languages. A person who speaks more than two languages is called “multilingual.” A person does not have to speak two languages with equal fluency to be considered bilingual; usually, a person will be stronger in one language than another. It is common for most of the world’s societies to be multilingual; in the United States, one in five children enters school speaking a language other than English, according to the 2000 Census. Some children who learn English in school speak their native language at home. Bilingualism often allows children to communicate with their grandparents, which can strengthen family bonds across both generations and countries.
Bilingualism teaches an appreciation of the arts and traditions of two cultures. It promotes tolerance and cross-cultural understanding; research indicates that children who are raised with a bicultural identity tend to be more accepting of cultural differences in others.
Yes. The average person has three or four dreams each night, with each dream lasting 10 minutes or more. Almost all dreams occur during REM sleep, a period of sleep characterized by fast breathing and heart rates. Scientists do not understand why dreaming is important, but one theory is that the brain is either cataloging the information it acquired during the day and discarding the data it does not want, or is creating scenarios to work through situations that may be causing emotional distress.
Like sleep, most people who are deprived of dreams become disoriented, are unable to concentrate, and may even have hallucinations. Sometimes it is hard to remember our dreams because they are stored in our short-term memory.
The fastest growing hairs on the human body are men’s beard hairs. If the average male never trimmed his beard, it would grow to almost 30 feet (9 meters) long in his lifetime.
A cord is a traditional unit of volume used to measure stacked firewood. In the United States, the cord is defined legally as the volume of a stack of firewood 4 feet (1.2 meter) wide, 8 feet (2.4 meter) long, and 4 feet (1.2 meter) high. (In Maryland, the law specifies that the wood be stacked “tight enough that a chipmunk cannot run through it.”) The name comes from an old method of measuring a stack of firewood using a cord or string.
In the U.S. timber industry, the cord is also used as a unit of weight for pulpwood. The weight varies with tree species, ranging from about 5,200 pounds (2,358 kilograms) for pine to about 5,800 pounds for hardwood.
Once in a while the Moon passes directly in front of the Sun as it makes its way around Earth. It temporarily blocks out the Sun, casting a shadow on a portion of Earth that is experiencing day.
When this total eclipse of the Sun—a solar eclipse occurs, the part of Earth affected becomes dark and cold until the Moon passes by. Surrounding areas experience a partial eclipse, when just part of the Sun is temporarily covered by the Moon.
The word shift means to change or rearrange, which is why we call those who work during differing blocks of time “shift workers.” This use of the word shift also applies to an individual’s ability to change or adapt.
Therefore, if you’re “shiftless” you lack the initiative or resources to change with the circumstances. On the other hand, someone who is “shifty” is too adept at change and isn’t to be trusted.