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In LaTeX ˇx is coded as "\check{x}" in math mode (You will occasionally hear mathematicians refer to the empty set as "phi" which is historically  - Information from abstractmath.org

In LaTeX ˇx is coded as "\check{x}" in math mode For these uses the LaTeX code for a∗ is "a^\ast" This symbol is called colon equals - Information from abstractmath.org

Logical Constructions A logical construction is a way of making a compound assertion whose truth depends only on the truth value of the assertion(s) it is  - Information from abstractmath.org

Note that plural indefinite descriptions do not use an article Example "Show that an integer that is divisible by four is divisible by two" - Information from abstractmath.org