Love is one of the most universally recognizable and revered emotions in the world. It has been portrayed in art for centuries and is a subject of many movies, songs and books. It’s also the reason you forgive your partner for being late, push yourself to complete a creative project and feel devastated when your favorite team loses. It’s a complex concept that’s difficult to define. While psychologists generally agree there are a few basic types of love, they disagree on whether it’s an emotion, state of being or a choice.

The word “love” comes from the Latin verb “amore,” which means “to love” or “be devoted to.” During Roman times, “love” became a synonym for passion and sexual desire. In the English language, it has many different definitions, including affection, friendship and attraction. The concept of love has been a major topic for philosophical, historical and scientific discussion throughout the ages.

While scientists and philosophers have argued over whether it’s an emotion, researchers have focused on understanding how people experience and communicate love. They have developed several theories to explain love and its variations, including the color wheel theory, the triangular theory and a model that incorporates intimacy, passion and commitment.

A person’s love style may be determined by their personality, genetics and past relationship experiences. For example, people high in dark traits, such as narcissism, psychopathy and machiavellianism, endorse more ludus and pragma love styles than those who are more emotionally sensitive and empathetic.

When a person falls in love, their brain becomes more active in areas associated with attachment, motivation and focus. A surge of dopamine, the brain’s feel-good chemical, is created during this process. In addition, a person’s heart rate increases and blood pressure rises.

In the long term, a person’s ability to sustain love may depend on how much they can give of themselves. This type of love is often referred to as agape, or self-sacrificing love. A person who loves agape often feels a sense of duty and a drive to help others.

Some people have a mixture of love styles, such as ludus and pragma plus agape and philia. People who love ludus and pragma may have a romantic attraction but also worry about committing to their partner, while those who love agape and philia feel a strong bond with friends that lasts for years.

Other forms of love are nonromantic, such as the closeness and attachment that can develop between family members or between people who work together. Similarly, pets can be loved by people who exhibit a combination of these love styles. In addition, people can be committed to a cause, such as a charitable organization, school or church. The idea of a lifelong practice of love may best be described by looking at the lives of people such as Martin Luther King Jr., Mahatma Gandhi and Oprah Winfrey, who have devoted themselves to helping others. These individuals have helped to shape the world in a positive way through their unyielding and selfless devotion to their beliefs and values.

Sleep does more than make you feel refreshed — it’s also hard at work, repairing muscles, sweeping away waste and forming memories. During slumber, hormones that play a role in everything from hunger to stress levels are released, so it’s no wonder people who regularly get less than a full night of rest have a higher risk for health problems like obesity, depression and diabetes. Luckily, getting more sleep can help reduce those risks, and there are plenty of tools to improve your slumber.

The human body requires a lot of sleep to function properly, and the amount needed varies from person to person and changes with age. Infants generally need about sixteen hours of sleep per day, while teenagers typically require about nine hours on average. Most adults need seven to eight hours a night. In addition to the age-related change from polyphasic sleep patterns (with several periods of waking and sleeping each day) to monophasic sleep, there is a gradual shift toward the concentration of sleep in one long nocturnal period with aging. This change probably reflects both the maturing of the brain and a cultural shift toward a schedule of daytime activity and nocturnal sleep.

Scientists know a lot about the physiological processes that occur during sleep, but there is still much we don’t understand. One of the most important discoveries was the discovery of a type of sleep called rapid eye movement (REM) sleep, which has characteristics that are more like activated wakefulness than other types of sleep. Scientists are now trying to figure out what the brain is doing during this time, and how it is related to mental and physical well-being.

Among the many benefits of getting enough sleep is improved cognition, which can mean better performance at school and on the job. Many studies have found that students who sleep less tend to have lower grades, mainly because they have trouble with concentration and abstract thinking. Adults who lack adequate slumber are also at greater risk for depression and anxiety disorders.

Sleep can help regulate your immune system, which is also an important aspect of maintaining good overall health. Research suggests that lack of sleep may contribute to the development of autoimmune conditions, such as rheumatoid arthritis and inflammatory bowel disease.

A growing body of evidence shows that a lack of sleep can also lead to insulin resistance, a condition characterized by high blood sugar levels and a decreased ability to use glucose as energy. This can lead to diabetes, which is a major risk factor for heart disease.

A poor diet and an excessively stressful lifestyle can disrupt your slumber, but there are many things you can do to improve your chances of getting enough quality sleep. The key is to establish a regular routine. Try to go to bed at around the same time each night, and avoid waking up in the middle of the night or sleeping too late on weekends. Avoid caffeine and other stimulants in the evening, and limit your screen time before bed. If you have a chronic illness, it is especially important to maintain good sleep habits because certain medications and treatments can interfere with your slumber.