Luck
Luck (also called fortuity) is a chance happening, or that which happens beyond a person's control. Luck can be good or bad.

# Luck as lack of control
Luck refers to that which happens beyond a person's control. This view incorporates phenomena that are chance happenings, a person's place of birth for example, but where there is no uncertainty involved, or where the uncertainty is irrelevant. Within this framework one can differentiate between three different types of luck:
- Constitutional luck, that is, luck with factors that cannot be changed. Place of birth and genetic constitution are typical examples.
- Circumstantial luck, that is, luck with factors that are haphazardly brought on. Accidents and epidemics are typical examples.
- Ignorance luck, that is, luck with factors one does not know about. Examples can be identified only in hindsight.

# Luck as a fallacy
Another view holds that "luck is probability taken personally".
A rationalist approach to luck includes the application of the rules of probability, and an avoidance of unscientific beliefs. The rationalist feels the belief in luck is a result of poor reasoning or wishful thinking. To a rationalist, a believer in luck commits the "post hoc, ergo propter hoc" logical fallacy, which argues that because two events are connected sequentially, they are connected causally as well:
A happens (luck-attracting event or action) and then B happens; 
Therefore, A caused B.
In this particular perspective, probability is only affected by confirmed causal connections. A brick falling on a person walking below, therefore, is not a function of that person's luck, but is instead the result of a collection of understood (or explainable) occurrences. Statistically, every person walking near the building was just as likely to have the brick fall on them.
The gambler's fallacy and inverse gambler's fallacy both explain some reasoning problems in common beliefs in luck. They involve denying the unpredictability of random events: "I haven't rolled a seven all week, so I'll definitely roll one tonight".
Luck is merely an expression noting an extended period of noted outcomes, completely consistent with random walk probability theory. Wishing one "good luck" will not cause such an extended period, but it expresses positive feelings toward the one -- not necessarily wholly undesirable.

# Luck as an essence
There is also a series of spiritual, or supernatural beliefs regarding fortune. These beliefs vary widely from one to another, but most agree that luck can be influenced through spiritual means by performing certain rituals or by avoiding certain circumstances.
One such activity is prayer, a religious practice in which this belief is particularly strong. Many cultures and religions worldwide place a strong emphasis on a person's ability to influence their fortune by ritualistic means, sometimes involving sacrifice, omens or spells. Others associate luck with a strong sense of superstition, that is, a belief that certain taboo or blessed actions will influence how fortune favors them for the future.
Luck can also be a belief in an organization of fortunate and unfortunate events. Luck is a form of superstition which is interpreted differently by different individuals.
Carl Jung described synchronicity: the "temporally coincident occurrences of acausal events". He described coincidences as an effect of a collective unconscious.
Christian and Islamic religions believe in the will of a supreme being rather than luck as the primary influence in future events. The degrees of this Divine Providence vary greatly from one person to another; however, most acknowledge providence as at least a partial, if not complete influence on luck. These religions, in their early development, accommodated many traditional practices. Each, at different times, accepted omens and practiced forms of ritual sacrifice in order to divine the will of their supreme being or to influence divine favoritism. The concept of "Divine Grace" as it is described by believers closely resembles what is referred to as "luck" by others.
Mesoamerican religions, such as the Aztecs, Mayans and Incas, had particularly strong beliefs regarding the relationship between rituals and luck. In these cultures, human sacrifice (both of willing volunteers and captured enemies) was seen as a way to please the gods and earn favor for the city offering the sacrifice. The Mayans also believed in blood offerings, where men or women wanting to earn favor with the gods, to bring about good luck, would cut themselves and bleed on the gods' altar.
Many traditional African practices, such as voodoo and hoodoo, have a strong belief in superstition. Some of these religions include a belief that third parties can influence an individual's luck. Shamans and witches are both respected yet feared, based on their ability to cause good or bad fortune for those in villages near them.

# Luck as a placebo
Some encourage the belief in luck as a false idea, but which may produce positive thinking, and alter one's responses for the better. Others, like Jean Paul Sartre and Sigmund Freud, feel a belief in luck has more to do with a locus of control for events in one's life, and the subsequent escape from personal responsibility. According to this theory, one who ascribes their travails to "bad luck" will be found upon close examination to be living risky lifestyles.
If "good" and "bad" events occur at random to everyone, believers in good luck will experience a net gain in their fortunes, and vice versa for believers in bad luck. This is clearly likely to be self-reinforcing. Thus, although untrue, a belief in good luck may actually be an adaptive meme.

# Numerology
Most cultures consider some numbers to be lucky or unlucky. This is found to be particularly strong in Asian cultures, where the obtaining of "lucky" telephone numbers, automobile license plate numbers, and household addresses are actively sought, sometimes at great monetary expense. Numerology, as it relates to luck, is closer to an art than to a science, yet numerologists, astrologists or psychics may disagree. It is interrelated to astrology, and to some degree to parapsychology and spirituality and is based on converting virtually anything material into a pure number, using that number in an attempt to detect something meaningful about reality, and trying to predict or calculate the future based on lucky numbers. Numerology is folkloric by nature and started when humans first learned to count. Through human history it was, and still is, practiced by many cultures of the world from traditional fortunetelling to on-line psychic reading. There are many variations of numerology - most are based on the Chaldean System or the Pythagorean System. Latest modern methods such as Formalogy also are in use. Most are contemporary systems of advanced numerology and rely on leading principals of numerology and related mystical traditions observed by Ancestral Armenians, Mesopotamians, Egyptians, Assyrians, Phoenicians, Persians, Hebrews, Greeks and Romans.

# Luck in Religion

## Judaism and Christianity
- But you who forsake Yahweh, who forget my holy mountain, who prepare a table for Fortune, and who fill up mixed wine to Destiny (Isaiah 65:11 - The bearing that this has on beliefs concerning luck is a matter of controversy)
- The lot is cast into the lap, but its every decision is from the Lord (Book of Proverbs 16:33 NIV)
- I have seen something else under the sun: The race is not to the swift or the battle to the strong, nor does food come to the wise or wealth to the brilliant or favor to the learned; but time and chance happen to them all.  (Ecclesiastes 9:11 NIV)