language of a machine

if $\text{[math]}$ is the set of all strings that machine $\text{[math]}$ accepts, we say that $\text{[math]}$ is the language of machine $\text{[math]}$ and write $\text{[math]}$ . we say that $\text{[math]}$ recognizes $\text{[math]}$ or that $\text{[math]}$ accepts $\text{[math]}$ . because the term accept has different meanings when we refer to machines accepting strings and machines accepting languages, we prefer the term recognize for languages in order to avoid confusion.
a machine may accept several strings, but it always recognizes only one language. if the machine accepts no strings, it still recognizes one language--namely, the empty language $\text{[math]}$ .
[cite:;taken from @sipser_comp_2012 chapter 1 regular languages]