It's Just A Theory!
Short Answer
Actually, evolution is both a theory and a fact. A fact is something we observe in the world, and a theory is our best explanation for it.
Stephen Jay Gould famously addressed this argument by pointing out that the fact of gravity is that things fall, and our theory of gravity began with Isaac Newton and was later replaced by Einstein's improved theory. The current state of our theory to explain gravity does not affect the fact that things fall. Similarly, Darwin's original theory of evolution was highly incomplete and had plenty of errors. Today's theory is still incomplete but it's a thousand times better than it was in Darwin's day. But the state of our explanation does not affect the observed fact that species evolve over time.
Long Answer
Creationists Mislead: Pretending Not To Know The Meaning of a Word
From Dictionary.com: the·o·ry [thee-uh-ree, theer-ee] noun, plural the·o·ries.
1 a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine.
2 a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact. Synonyms: idea, notion hypothesis, postulate. Antonyms: practice, verification, corroboration, substantiation.
Here's the Detailed Explanation
In English, words often have more than one meaning
Homographs are words spelt the same but with different meanings -
context tells you which one is relevant:
EYE in your face, EYE of a hurricane, EYE in a potato
FINE meaning good FINE a penalty for speeding
BAT a flying mammal or a cricket BAT
DOWN the hill or DOWN on a ducks back
ROW a fight or ROW a line or ROW a boat
PRESENT time is now or a PRESENT for xmas
This is a Bridge with a capital B
This is a bridge
These are Peers (of the Realm) with capital P
This is a (group of) peers
This is a Strike with a capital S
It is different to a strike
The words are the same but they don't mean the same. If someone tried to tell you they were the same, you'd realize either he was very stupid, or he thought you were stupid enough to believe him
This is a theory with a small 't'
(Sherlock Holmes has a theory about the crime)
This is a scientific Theory with a capital T
It explains the facts, and predicts that new facts will fit the explanation
This is superstition
This is how silly it is
Perhaps the most extreme example of the difference a Capital letter makes is the former Catholic Archbishop of Manila, Jaime Lachica Sin, who was made a Cardinal by Pope Paul VI in 1976. Wikipedia helpfully explains that Cardinal Sin should not be confused with "cardinal sin" (being the 'seven deadly sins'). His title and surname as Cardinal Sin were the source of many jokes in the Philippines and the Philippine Catholic community, such as "The greatest sin of all...Cardinal Sin", and his own pun: "Welcome to the house of Sin" referring to his official residence, Villa San Miguel.
And to Sum It Up Again
From Dictionary.com:
the·o·ry [thee-uh-ree, theer-ee]
noun, plural the·o·ries.
1 a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine.
2 a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact.
