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.
The noun XI has 2 senses: 1. the cardinal number that is the sum of ten and one. 2. the 14th letter of the Greek alphabet. Familiarity information: XI used as a noun is rare. â¢ XI (adjective). The adjective XI has 1 sense: 1. being one more than ten. Familiarity information: XI used as an adjective is very rare.