Theme of this puzzle, seen seven times in the grid

Question:

Length:

Similar Crossword Questions:

Number of times this puzzle's theme word appears diagonally in the grid (to complete the puzzle, shade those words plus the Down answers that begin where they meet)
Puzzle theme which appears nine more times in the grid
Theme of this puzzle, whose members are hidden throughout the grid
First of a pair of letters swapped six times in this puzzle's theme entries
Word appearing eight times in this puzzle grid
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Decorative physical changes, and a hint to this puzzle's theme
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What each completed pair of theme answers in this puzzle is
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Physical principle whose equation explains the changes in this puzzle's theme entries
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Find new work - or what you must do to get the three theme entries' names in this puzzle