math bold fonts
\( {\mathbf a b c d e f g h i j k l m n o p q r s t u v w x y z }\)
\({\mathbf {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z}} \)
math script fonts
$ \mathscr {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z} $
math calligraphic fonts
$ { \mathcal {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z}} $
math black board fonts
${\mathbb {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z}} $
Usage
For \(\xbf ,\ybf \) etc type ({\mathbf x}, {\mathbf y} ..) etc
For \( \Asc, \Bsc,... \) type \mathscr A, \mathscr B .... etc
For \(\Aca \Bca, ... \) etc type \mathcal A, \mathcal B etc.
For \(\Abb, \Bbb,... \) etc type (\mathbb A ,\mathbb B )
Try \(\mathbb X \qquad \mathcal x \qquad \mathscr X \qquad \mathbf x \qquad \mathbf X\)