Evolution
Evolution is a fact. The theory of evolution by natural selection is what you are trying to talk about. When someone says " evolution is just a theory " they are using the vulgar, common sense of the word theory. They mean guess, hunch and the like. The theory of evolution by natural selection is in the scientific sense of the word theory, which means a body of explanatory work supported by myriad lines of converging evidence that has been tested rigouusly and replicated often. Any good dictionary uses this scientific meaning of theory as the primary meaning of the word.
Darwin has a theory of Survival of the Fittest.
The word 'theory' means it is an explanatory framework for some set of observational data. As to your question: while there is an overwhelming amount of observational data supporting the general tenets of evolutionary theory, and it is now impossible to rationally reject these tenets, it will technically always remain an explanatory model - a theory.
Another word that can be used instead of vacuole is cavity. Both are a small hole, filled with fluid.
Holistic theory
supposition
Evolution
Hypothesis may be the word you are looking for.
The word hypothesis is another word for an educated guess.Similar terms include theory and speculation.
Proposal. A thesis is the proposal of a theory. It's the seed from which your essay blossoms.
Trait theory
If you are asking the expansion of the word chess, there is none. The word chess is believed to have originated from the Sanskrit word "chaturanga". Another well-accepted theory about the origin of the word is that it is a modification of the Persian word "shah".
The correct spelling is 'theory'.
The Big Bang Theory
The Latin word for theory is the word theoria. In Spanish this word is said as teoria and in the French language it is said as theorie.
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