Sadness is emotional pain associated with, or characterized by feelings of disadvantage, loss, despair, helplessness, sorrow, and rage. These feelings of certain things are usually negative. When one is sad, people often become outspoken, less energetic, and emotional. Crying is an indication of sadness.

Sadness can be viewed as a temporary lowering of mood, whereas depression is more chronic.

Sadness is one of Paul Ekman's "six basic emotions - happy, sad, angry, surprised, afraid, disgusted".

'Being sad is a common experience in childhood. If faced openly, sadness can help families become stronger and more able to handle painful feelings'. On the other hand, some families may have the (conscious or unconscious) rule: 'No sadness allowed...we were not allowed to be sad...a matter of family pride'. The problem may then be that 'that screened-off emotion isn't available to us when we need it....the loss of sadness makes us a bit manic'.

Sadness is part of the normal process of the child separating from an early symbiosis with the mother and becoming more independent. 'Every time a child separates just a tiny bit more, he'll have to cope with a small loss. He'll have to get sad for a little bit'; and if the mother cannot bear this, 'if she dashes right in to relieve the child's distress every single time he shows any...the child is not getting a chance to learn how to cope with sadness'. This is why 'trying to jostle or joke out of a sad mood is devaluing to her' or him: 'we need to respect a child's right to experience a loss fully and deeply'.

A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun, also known as daytime. The period of time measured from local noon to the following local noon is called a solar day.

Several definitions of this universal human concept are used according to context, need and convenience. In 1967, the second was redefined in terms of the wavelength of light, and it became the SI base unit of time. The unit of measurement for time called "day", redefined in 1967 as 86,400 SI seconds and symbolized d, is not an SI unit, but it is accepted for use with SI. A civil day is usually also 86,400 seconds, plus or minus a possible leap second in Coordinated Universal Time UTC, and, in some locations, occasionally plus or minus an hour when changing from or to daylight saving time. The word day may also refer to a day of the week or to a calendar date, as in answer to the question "On which day?" Day also refers to the part of the day that is not night — also known as 'daytime'. The life patterns of humans and many other species are related to Earth's solar day and the cycle of day and night (see circadian rhythms).

Angels, in a variety of religions, are regarded as spirits. They are often depicted as messengers of God in the Hebrew and Christian Bibles and the Quran. The English word angel is derived from the Greek ἄγγελος (aggelos), a translation of מלאך (mal'akh) in the Hebrew Bible (Tanakh); a similar term, ملائكة (Malāīkah), is used in the Qur'an. The Hebrew and Greek words originally meant messenger, and depending on the context may refer either to a human messenger (possibly a prophet or priest, such as Malachi, "my messenger", but also for more mundane characters, as in the Greek superscription that the Book of Malachi was written "by the hand of his messenger" (ἀγγήλου)) or to a supernatural messenger, such as the "Mal'akh YHWH," who (depending on interpretation) is either a messenger from God, an aspect of God (such as the Logos), or God Himself as the messenger (the "theophanic angel.")

The term "angel" has also been expanded to various notions of spirits found in many other religious traditions. Other roles of angels include protecting and guiding human beings, and carrying out God's tasks.