The most common and most likely answer to this crossword clue is the 10 letter word RELATIVITY
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More clues leading to the result RELATIVITY
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The cryptic/wordplay part
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What does RELATIVITY mean?
RELATIVITY noun- The state of being relative to something else.
- The principle that the laws of physics should be the same for all observers.
- Either of two theories (special relativity or general relativity) developed by German-American physicist Albert Einstein. Also called Einsteinian relativity.