Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses"; "true in fact and theory"
Hypothesis: a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"
Observation: any information collected with the senses
Data: factual information, especially information organized for analysis or used to reason or make decisions
Fact: when an observation is confirmed repeatedly and by many independent and competent observers, it can become a fact
Belief: any cognitive content (perception) held as true; religious faith
Impression: a vague idea in which some confidence is placed; "his impression of her was favorable"; "what are your feelings about the crisis?"; "it strengthened my belief in his sincerity"; "I had a feeling that she was lying"
All the terms used in science
Take their meanings
Totally
From the operations of observation
Employed by an observer
In measuring that thing or event
Named by The Word.
No other kind of meaning
Has any meaning
In science.