I found in a text, the following notation:
$\lbrace 1, 2, 3, 4 \rbrace\cap 2= \lbrace 2 \rbrace$
To my knowledge, a set and an element cannot be concatenated by a set intersection i.e., the set intersection is defined for two sets, but neither for two elements nor for combining a set and an element. Therefore, the correct notation i think for the above line is
$\lbrace 1, 2, 3, 4 \rbrace\cap \lbrace 2\rbrace= \lbrace 2 \rbrace$.