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.
Meanings of the Letter X, Esoteric and Otherwise. X is a mark, an indicator, an identifier - one leaves their X mark as the signature of an illiterate or incapacitated - indicates where to sign on a form - marks the checkbox, the ballot. X represents 24 in arcane use as the 24th letter of the alphabet. X is a symbol for multiplication. In a coordinate system, the x-axis is the horizontal of the x, y and z. X indicates added dimension, by as a 2x4.