It is usually used as a representation of numeric fields, such as real number fields and complex number fields.

Package name amssymb

Usage \mathbb{}

Examples \mathbb{C}, \mathbb{R}

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Often used to represent space or transformation.

Package name mathrsfs

Usage \mathscr{}

Examples \ mathscr {x}, \ mathscr {y}, \ mathscr {a}

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This font is used in the set of all linear operators in functional analysis, so it should also be a conventional representation of space. Let's talk about it later. Leave it alone.

Package name amssymb

Usage \ Mathematics {}

Example \mathcal{L}

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This font is used for all compact operators.

Package name amssymb

Usage \mathfrak{}

Example \mathfrak{C}

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