At the core of biology and other sciences lies a problem-solving approach called the scientific method. 1  Make an observation. 2  Ask a question. 3  Form a hypothesis, or testable explanation. 4  Make a prediction based on the hypothesis.  Test the prediction.
Xi. Xi is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh. Xi is not to be confused with the letter chi, which gave its form to the Latin letter X.
Even the ubiquitous [math]\pi[/math] has meanings other than that of the ratio of a circle's circumference to its diameter. http://en.wikipedia.org/wiki/The... Theta is just a Greek letter used often with angles and with polar coordinates as a substitute variable, not unlike the fabled x in algebra. Neither theta nor x have any special meaning except with a particular context.