Panic is a sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an animalistic fight-or-flight reaction. Panic may occur singularly in individuals or manifest suddenly in large groups as mass panic (closely related to herd behavior).

The word panic derives from the Greek πανικός, "pertaining to shepherd god Pan", who took amusement from frightening herds of goats and sheep into sudden bursts of uncontrollable fear. The ancient Greeks credited the battle of Marathon's victory to Pan, using his name for the frenzied, frantic fear exhibited by the fleeing enemy soldiers.

Prehistoric men used mass panic as a technique when hunting animals, especially ruminants. Herds reacting to unusually strong sounds or unfamiliar visual effects were directed towards cliffs, where they eventually jumped to their deaths when cornered. Humans are also vulnerable to panic and it is often considered infectious, in the sense one person's panic may easily spread to other people nearby and soon the entire group acts irrationally, but people also have the ability to prevent and/or control their own and others' panic by disciplined thinking or training (such as disaster drills). Architects and city planners try to accommodate the symptoms of panic, such as herd behavior, during design and planning, often using simulations to determine the best way to lead people to a safe exit and prevent congestion (stampedes). The most effective methods are often non-intuitive. A tall column, approximately 1 ft (300 mm) in diameter, placed in front of the door exit at a precisely calculated distance, may speed up the evacuation of a large room by up to 30%, as the obstacle divides the congestion well ahead of the choke point.

The present (or now) is the time that is associated with the events perceived directly and in the first time, not as a recollection (perceived more than once) or a speculation (predicted, hypothesis, uncertain). It is a period of time between the past and the future, and can vary in meaning from being an instant to a day or longer. In radiocarbon dating, the "present" is defined as AD 1950.

It is sometimes represented as a hyperplane in space-time, typically called "now", although modern physics demonstrates that such a hyperplane can not be defined uniquely for observers in relative motion. The present may also be viewed as a duration (see specious present).

Contemporary history describes the historical timeframe that is immediately relevant to the present time and is a certain perspective of modern history.

The present is contrasted with the past and the future. Modern physics has not yet been able to explain the perceived aspect of 'the present' as 'eliminator of possibilities' that transfers future into past. A complicating factor is that whilst a given observer would describe 'the present' as a spatial structure with a zero-length time lapse, other observers would associate both time and space to this structure and therefore disagree on what constitutes 'the present'.

Data ( /ˈdeɪtə/ DAY-tə, /ˈdætə/ DA-tə, or /ˈdɑːtə/ DAH-tə) are values of qualitative or quantitative variables, belonging to a set of items. Data in computing (or data processing) are often represented by a combination of items organized in rows and multiple variables organized in columns. Data are typically the results of measurements and can be visualised using graphs or images. Data as an abstract concept can be viewed as the lowest level of abstraction from which information and then knowledge are derived. Raw data, i.e., unprocessed data, refers to a collection of numbers, characters and is a relative term; data processing commonly occurs by stages, and the "processed data" from one stage may be considered the "raw data" of the next. Field data refers to raw data collected in an uncontrolled in situ environment. Experimental data refers to data generated within the context of a scientific investigation by observation and recording.

The word data is the plural of datum, neuter past participle of the Latin dare, "to give", hence "something given". In discussions of problems in geometry, mathematics, engineering, and so on, the terms givens and data are used interchangeably. Such usage is the origin of data as a concept in computer science or data processing: data are numbers, words, images, etc., accepted as they stand.